A police officer wears a mourning band on his badge kept next to his gun during a candlelight vigil at Dallas City Hall following the multiple police shootings in Dallas, Texas, U.S., July 11, 2016. REUTERS/Carlo Allegri 

A Dallas police detective wears a mourning band on his badge kept next to his SIG Sauer gun during a candlelight vigil at Dallas City Hall following the multiple police shootings in Dallas, Texas, U.S., July 11, 2016. REUTERS/Carlo Allegri 

A French plainclothes policeman apprehends a demonstrator as protests continue against the labour reforms law in Nantes, France, June 9, 2016. REUTERS/Stephane Mahe TPX IMAGES OF THE DAY

A French plainclothes policeman apprehends a demonstrator as protests continue against the labour reforms law in Nantes, France, June 9, 2016. REUTERS/Stephane Mahe

A French plainclothes policeman apprehends a demonstrator as protests continue against the labour reforms law in Nantes, France, June 9, 2016. REUTERS/Stephane Mahe

French plainclothes police apprehend a demonstrator near CRS riot police as protests continue against the labour reforms law in Nantes, France, June 9, 2016. REUTERS/Stephane Mahe

Plainclothes police officers check identification cards of the residents as they flee after clashes between security forces and Kurdish militants from Baglar district, which is partially under curfew, in the Kurdish-dominated southeastern city of Diyarbakir, Turkey March 15, 2016. REUTERS/Sertac Kayar 

Men in plain clothes detain a supporter of Uganda's leading opposition party Forum for Democratic Change as police and military forces disperse their procession with their presidential candidate to a campaign ground in Kampala, Uganda, February 15, 2016. REUTERS/James Akena 

A suspect is detained by plain clothes police during a raid at a house in the Kreuzberg district of Berlin, Germany February 4, 2016. German police conducted raids in Berlin and other parts of northern Germany on Thursday in a search for four men suspected of links to Islamic State militants and possibly preparing an attack in Germany, police said. REUTERS/Fabrizio Bensch

A suspect is detained by plain clothes police during a raid at a house in the Kreuzberg district of Berlin, Germany February 4, 2016. German police conducted raids in Berlin and other parts of northern Germany on Thursday in a search for four men suspected of links to Islamic State militants and possibly preparing an attack in Germany, police said. REUTERS/Fabrizio Bensch TPX IMAGES OF THE DAY

A suspect is detained by plain clothes police during a raid at a house in the Kreuzberg district of Berlin, Germany February 4, 2016. German police conducted raids in Berlin and other parts of northern Germany on Thursday in a search for four men suspected of links to Islamic State militants and possibly preparing an attack in Germany, police said. REUTERS/Fabrizio Bensch

A suspect is detained by plain clothes police during a raid at a house in the Kreuzberg district of Berlin, Germany February 4, 2016. German police conducted raids in Berlin and other parts of northern Germany on Thursday in a search for four men suspected of links to Islamic State militants and possibly preparing an attack in Germany, police said. REUTERS/Fabrizio Bensch

A suspect is detained by plain clothes police during a raid at a house in the Kreuzberg district of Berlin, Germany February 4, 2016. German police conducted raids in Berlin and other parts of northern Germany on Thursday in a search for four men suspected of links to Islamic State militants and possibly preparing an attack in Germany, police said. REUTERS/Fabrizio Bensch

A suspect is detained by plain clothes police during a raid at a house in the Kreuzberg district of Berlin, Germany February 4, 2016. German police conducted raids in Berlin and other parts of northern Germany on Thursday in a search for four men suspected of links to Islamic State militants and possibly preparing an attack in Germany, police said. REUTERS/Fabrizio Bensch TPX IMAGES OF THE DAY

A suspect is detained by plain clothes police during a raid at a house in the Kreuzberg district of Berlin, Germany February 4, 2016. German police conducted raids in Berlin and other parts of northern Germany on Thursday in a search for four men suspected of links to Islamic State militants and possibly preparing an attack in Germany, police said. REUTERS/Fabrizio Bensch

Residents (R) carry their belongings as they flee from Sur district, which is partially under curfew, in the Kurdish-dominated southeastern city of Diyarbakir, Turkey January 27, 2016. Security forces killed 20 Kurdish militants in southeast Turkey while three Turkish soldiers died in a rebel attack, the military said on Wednesday, as authorities widened a curfew in the mainly Kurdish region's largest city, Diyarbakir. Hundreds of locals, including children and the elderly, fled curfew-bound areas of Diyarbakir's Sur district as gunfire and blasts resounded and police helicopters flew overhead, a Reuters witness said. REUTERS/Sertac Kayar

Undercover Israeli security personnel detain a Palestinian protester during clashes with Israeli troops in the West Bank city of Bethlehem, January 22, 2016. REUTERS/Abdelrahman Younis

A plain-clothes police officer stands guard at a crime scene where a man was shot dead at La Tiendona Market in San Salvador, El Salvador on July 2, 2015. In El Salvador the number of homicides surged 70 percent last year, making the central American nation among the most violent countries in the world. Violence and murders have risen steadily since a 2012 truce between the two main street gangs began to fall apart. Months of reporting show killings in the suburbs of the capital, San Salvador, where powerful gangs known as maras control entire neighbourhoods. REUTERS/Jose Cabezas PICTURE 5 OF 35 - SEARCH "CABEZAS MURDER" FOR ALL IMAGES 

A flag is seen at half-staff outside a home honoring NYPD Detective Joseph Lemm down the street from the 50th precinct in the Bronx borough of New York December 22, 2015. Six American troops, including Lemm, a 15-year veteran of the NYPD who also volunteered in the U.S. Air National Guard and was on his third deployment to war zones, were killed Monday when a suicide bomber on a motorbike struck their patrol in the deadliest attack on U.S. forces this year. REUTERS/Shannon Stapleton 

A bunting honoring NYPD Detective Joseph Lemm hangs above the entrance to the 50th precinct in the Bronx borough of New York December 22, 2015. Six American troops, including Lemm, a 15-year veteran of the NYPD who also volunteered in the U.S. Air National Guard and was on his third deployment to war zones, were killed Monday when a suicide bomber on a motorbike struck their patrol in the deadliest attack on U.S. forces this year. REUTERS/Shannon Stapleton 

A plainclothes policeman sits and smokes a cigarette in front of the restaurant that was attacked this morning in Cairo, Egypt, December 4, 2015. A Molotov cocktail hurled at the Cairo restaurant killed 16 people and wounded two on Friday, Egyptian security officials said. REUTERS/Mohamed Abd El Ghany TPX IMAGES OF THE DAY

Plainclothes police officers perform a security check in front of a barrier during an operation in Sur district, where an unidentified gunman last Saturday killed a top Kurdish lawyer, in the Kurdish-dominated southeastern city of Diyarbakir, Turkey, December 2, 2015. REUTERS/Sertac Kayar

New York City Police Department Commisioner Commissioner William J. Bratton presents the new detective shield of slain New York City police (NYPD) Randolph Holder, who was posthumously promoted, to Holder's father during the funeral service in New York October 28, 2015. Thousands of police officers waited in the rain to pay their respects at Wednesday's funeral for Holder, who was shot and killed while on patrol a week ago. REUTERS/Mary Altaffer/Pool 

Undercover Israeli security personnel and Israeli soldiers take position during clashes with Palestinians near the Jewish settlement of Bet El, near the West Bank city of Ramallah October 7, 2015. Israeli Prime Minister Benjamin Netanyahu has cancelled a trip to Germany planned for Thursday, German government sources told Reuters, as tensions rise between Palestinians and Israelis after about 10 days of violence. REUTERS/Mohamad Torokman 

Undercover Israeli security personnel and Israeli soldiers detain a wounded Palestinian protester during clashes near the Jewish settlement of Bet El, near the West Bank city of Ramallah October 7, 2015. Israeli Prime Minister Benjamin Netanyahu has cancelled a trip to Germany planned for Thursday, German government sources told Reuters, as tensions rise between Palestinians and Israelis after about 10 days of violence. REUTERS/Mohamad Torokman 

Undercover Israeli security personnel (R) and Israeli soldiers detain a wounded Palestinian protester during clashes near the Jewish settlement of Bet El, near the West Bank city of Ramallah, October 7, 2015. Israeli Prime Minister Benjamin Netanyahu has cancelled a trip to Germany planned for Thursday, German government sources told Reuters, as tensions rise between Palestinians and Israelis after about 10 days of violence. REUTERS/Mohamad Torokman TPX IMAGES OF THE DAY

Police escort a suspect identified, only with an initial "MJ", in front of the media at the police headquarters in Jakarta, Indonesia, September 11, 2015. The security guard was arrested in connection with the murder of Japanese national Yoshimi Nishimura, who was found dead in her apartment this week. Police have not officially charged the suspect but Jakarta Metropolitan Police Chief Tito Karnavian said the suspect could face the death penalty if found guilty of murder. REUTERS/Darren Whiteside

Plainclothes policemen stand next to a statue after students supporting the opposition attached mock ballots with option 'No' selected to it during a protest against the military-backed draft constitution in Bangkok, Thailand September 5, 2015. The junta-appointed National Reform Council (NRC) will vote on the draft on Sept. 6 and if it passes, it will be put to a referendum in January. It needs the support of just over half the NRC's 247 members. REUTERS/Jorge Silva 

Hasan Ali Saleh, 25, a suspected Syrian smuggler, talks to his mother Zahra Saleh (L) as he is escorted by a plainclothes Turkish police officer upon his arrival to the courthouse in Bodrum,, Turkey, September 4, 2015. Four suspected Syrian human traffickers detained in connection with the deaths of 3-year old Aylan Kurdi and his family appeared in handcuffs at a courthouse in Bodrum on Friday. Kurdi, washed up on a beach near the Turkish resort of Bodrum sparked a global outpouring of sympathy, and shocked European governments into renewed focus on tackling the migrant crisis. The United Nations refugee agency estimates more than 300,000 people have already used dangerous sea-routes this year to reach Europe this year alone, with around 2,500 losing their lives. REUTERS/Murad Sezer

Zahra Saleh, the mother of Hasan Ali Saleh, 25, a suspected Syrian smuggler, kisses her son as he is escorted by a plainclothes Turkish police officer upon his arrival to the courthouse in Bodrum, Turkey, September 4, 2015. Four suspected Syrian human traffickers detained in connection with the deaths of 3-year old Aylan Kurdi and his family appeared in handcuffs at a courthouse in Bodrum on Friday. Kurdi, washed up on a beach near the Turkish resort of Bodrum sparked a global outpouring of sympathy, and shocked European governments into renewed focus on tackling the migrant crisis. The United Nations refugee agency estimates more than 300,000 people have already used dangerous sea-routes this year to reach Europe this year alone, with around 2,500 losing their lives. REUTERS/Murad Sezer TPX IMAGES OF THE DAY 

Hasan Ali Saleh, 25, a suspected Syrian smuggler, talks to his mother Zahra Saleh (L) as he is escorted by a plainclothes Turkish police officer upon his arrival to the courthouse in Bodrum,, Turkey, September 4, 2015. Four suspected Syrian human traffickers detained in connection with the deaths of 3-year old Aylan Kurdi and his family appeared in handcuffs at a courthouse in Bodrum on Friday. Kurdi, washed up on a beach near the Turkish resort of Bodrum sparked a global outpouring of sympathy, and shocked European governments into renewed focus on tackling the migrant crisis. The United Nations refugee agency estimates more than 300,000 people have already used dangerous sea-routes this year to reach Europe this year alone, with around 2,500 losing their lives. REUTERS/Murad Sezer

Hasan Ali Saleh, 25, a suspected Syrian smuggler, talks to his mother Zahra Saleh (L) as he is escorted by a plainclothes Turkish police officer upon his arrival to the courthouse in Bodrum,, Turkey, September 4, 2015. Four suspected Syrian human traffickers detained in connection with the deaths of 3-year old Aylan Kurdi and his family appeared in handcuffs at a courthouse in Bodrum on Friday. Kurdi, washed up on a beach near the Turkish resort of Bodrum sparked a global outpouring of sympathy, and shocked European governments into renewed focus on tackling the migrant crisis. The United Nations refugee agency estimates more than 300,000 people have already used dangerous sea-routes this year to reach Europe this year alone, with around 2,500 losing their lives. REUTERS/Murad Sezer

Suspected Syrian smugglers are escorted by plainclothes Turkish police officers upon their arrival to the courthouse in Bodrum, Turkey, September 4, 2015. Four suspected Syrian human traffickers detained in connection with the deaths of 3-year old Aylan Kurdi and his family appeared in handcuffs at a courthouse in Bodrum on Friday. Kurdi, washed up on a beach near the Turkish resort of Bodrum sparked a global outpouring of sympathy, and shocked European governments into renewed focus on tackling the migrant crisis. The United Nations refugee agency estimates more than 300,000 people have already used dangerous sea-routes this year to reach Europe this year alone, with around 2,500 losing their lives. REUTERS/Murad Sezer

Suspected Syrian smugglers are escorted by plainclothes Turkish police officers upon their arrival to the courthouse in Bodrum, Turkey, September 4, 2015. Four suspected Syrian human traffickers detained in connection with the deaths of 3-year old Aylan Kurdi and his family appeared in handcuffs at a courthouse in Bodrum on Friday. Kurdi, washed up on a beach near the Turkish resort of Bodrum sparked a global outpouring of sympathy, and shocked European governments into renewed focus on tackling the migrant crisis. The United Nations refugee agency estimates more than 300,000 people have already used dangerous sea-routes this year to reach Europe this year alone, with around 2,500 losing their lives. REUTERS/Murad Sezer

Two plainclothes police officers leave an office of Koza Ipek Group in Ankara, Turkey, September 1, 2015, as a company official stands at the entrance during a police raid. Turkish police raided the offices of the conglomerate with close links to U.S.-based Muslim cleric Fethullah Gulen, an ally-turned-foe of President Tayyip Erdogan, company officials said on Tuesday. REUTERS/Umit Bektas

A paramilitary police officer in plain-clothes holding an umbrella keeps watch on Beijing's Tiananmen Square, August 27, 2015. Major Western leaders will not attend a military parade in China next week to mark the end of World War Two, leaving President Xi Jinping to stand with leaders and officials from Russia, Sudan, Venezuela and North Korea at his highest-profile event of 2015. REUTERS/Jason Lee

A paramilitary police officer in plain-clothes holding an umbrella keeps watch on Beijing's Tiananmen Square, August 27, 2015. Major Western leaders will not attend a military parade in China next week to mark the end of World War Two, leaving President Xi Jinping to stand with leaders and officials from Russia, Sudan, Venezuela and North Korea at his highest-profile event of 2015. REUTERS/Jason Lee

A paramilitary police officer in plain-clothes holding an umbrella keeps watch on Beijing's Tiananmen Square, August 27, 2015. Major Western leaders will not attend a military parade in China next week to mark the end of World War Two, leaving President Xi Jinping to stand with leaders and officials from Russia, Sudan, Venezuela and North Korea at his highest-profile event of 2015. REUTERS/Jason Lee

A Venezuelan border official, allows access into Venezuela to a family, after he checks their IDs, while they cross the Simon Bolivar bridge on the border with Colombia, at San Antonio in Tachira state, Venezuela, August 26, 2015. Hundreds of Colombians waded across a border river with fridges, chickens and mattresses on their backs as goats and children followed under the scorching tropical sun, victims of an escalating dispute with Venezuela's government. Saying they were forced from their rickety wooden or corrugated metal homes and scared of what might happen next if they stayed inside Venezuela, they fled across the River Tachira and back into their homeland on Tuesday. REUTERS/Carlos Garcia Rawlins 

A plainclothes policeman arrives the scene after a shooting incident near the entrance to Dolmabahce Palace in Istanbul, Turkey August 19, 2015. Turkish police detained two suspects with automatic weapons after a shooting on Wednesday near the entrance to Istanbul's Dolmabahce Palace, popular with tourists and home to the prime minister's Istanbul offices, the Dogan news agency said. REUTERS/Murad Sezer

Israeli police officers detain a right-wing activist during a counter-protest against supporters of hunger-striking Palestinian detainee Mohammed Allan, in the southern city in Ashkelon, August 16, 2015. The Palestinian detainee in the ninth week of his hunger strike fell unconscious at an Israeli hospital on Friday in a case that could test Israel's new force-feeding law. REUTERS/Amir Cohen 

New York City Police department (NYPD) officers stand near police tape at the site where two men were apparently shot outside a smoke shop Tuesday on Anderson Avenue, in the Bronx borough of New York, August 4, 2015. Illegal synthetic marijuana, or "weaponized" marijuana as police are calling it, is spreading across New York, particularly the city's homeless population in search of a cheap high but who often wind up hospitalized or dead. Picture taken August 4, 2015. REUTERS/Mike Segar 

A plainclothes police officer provides security at an event celebrating the 50th anniversary of the Voting Rights Act of 1965 in Washington July 30, 2015. REUTERS/Gary Cameron 

An Ethiopian soldier (L) and U.S. Secret Service agent guard a doorway at the National Palace as Ethiopia's Prime Minister Hailemariam Desalegn welcomed U.S. President Barack Obama for a bilateral meeting in Addis Ababa, Ethiopia July 27, 2015. President Obama is on a two-country tour of Africa. REUTERS/Jonathan Ernst 

France's President Francois Hollande (C) listens to policemen in the car park of a police station after drugs were found in a truck (unseen) in Marseille, France, July 27, 2015. REUTERS/Bertrand Langlois/Pool 

France's President Francois Hollande (L), flanked by France's Interior Minister Bernard Cazeneuve (2ndL) listens to a policeman in a police station after drugs were found in a truck in Marseille, France, July 27, 2015. REUTERS/Bertrand Langlois/Pool 

France's President Francois Hollande (C), flanked by French Junior Minister for Veterans and Memory Jean-Marc Todeschini (C,background) speaks to policemen after drugs were found in a truck in Marseille, France, July 27, 2015. REUTERS/Bertrand Langlois/Pool 

France's President Francois Hollande (2ndL), flanked by Provence-Alpes-Cote d'Azur regional council president Michel Vauzelle (L), listens to policemen, after drugs were found in a truck in Marseille, France, July 27, 2015. REUTERS/Bertrand Langlois/Pool 

France's President Francois Hollande (2ndL), flanked by Central director of French Judiciary Police Mireille Ballestrazzi (L), listens to policemen, after drugs were found in a truck in Marseille, France, July 27, 2015. REUTERS/Bertrand Langlois/Pool 

Protestors accost a plainclothes policemen as they march towards Batasang Pambansa in Quezon city, Metro Manila in the Philippines July 27, 2015. Aquino will address the joint session of Congress delivering his last State of the Nation at the Batasang Pambansa this afternoon. REUTERS/Erik De Castro 

A plainclothes policeman stands guard following an attack on police officers in Diyarbakir, Turkey, July 23, 2015. A Turkish police officer was shot and killed and a second wounded on Thursday in the mainly Kurdish city of Diyarbakir in the latest in a series of attacks that began with a suicide bombing blamed on Islamic State, security sources said. The shooting, which occurred in the centre of Diyarbakir, comes one day after two police officers were killed in an attack in Ceylanpinar on the Syrian border for which militants from the Kurdistan Workers Party (PKK) claimed responsibility. REUTERS/Sertac Kayar 

Investigators work at the site of a small explosion in a locker at the Kazansky railway station in Moscow, Russia, July 16, 2015. The small explosion in the locker occurred due to a faulty cooling box, according to Russian Interior Ministry. REUTERS/Tatyana Makeyeva 

Explosion experts assess the wreckage of a car, which belonged to an intelligence security officer, after it was destroyed in a blast in the Hamar Weyne district of Somalia's capital Mogadishu July 5, 2015. The officer and a policeman were injured in the explosion, according to a government official at the scene. REUTERS/Feisal Omar

Police officers control the crowd (rear) while surrounding a man (front C) suspected to be involved in opening fire on a beachside hotel in Sousse, Tunisia, as a woman reacts(R), June 26, 2015. At least 27 people, including foreign tourists, were killed when at least one gunman opened fire on a Tunisian beachside hotel in the popular resort of Sousse on Friday, an interior ministry spokesman said. Police were still clearing the area around the Imperial Marhaba hotel and the body of one gunman lay at the scene with a Kalashnikov assault rifle after he was shot in an exchange of gunfire, a security source at the scene said. REUTERS/Amine Ben Aziza TPX IMAGES OF THE DAY

Police officers destroy seized drugs with fire at an event to mark International Day against Drug Abuse and Illicit Trafficking, outside Yangon June 26, 2015. The government destroyed $155 million worth of drugs in Yangon, according to the organizers. REUTERS/Soe Zeya Tun

ATTENTION EDITORS - VISUAL COVERAGE OF SCENES OF DEATH OR INJURY

A policeman shows his badge while approaching a man who had just shot himself in front of the Capitol in Washington DC, as tourists react April 11, 2015. A man shot himself dead near the U.S. Capitol on Saturday, police said, sparking a temporary security lockdown at the complex on one of the busiest days for tourists in Washington. Picture taken April 11, 2015. REUTERS/Evan El-Amin TPX IMAGES OF THE DAY

A plain clothes California Highway Patrol detective, who had been marching with anti-police demonstrators, aims his gun at protesters after some in the crowd identified him and his partner during an arrest in Oakland, California, December 10, 2014. Chief Avery Browne, commander of the California Highway Patrol's Golden Gate Division, said two plainclothes CHP detectives were surrounded by up to 50 demonstrators who ignored orders to back off, despite one of the officers first taking out his baton and identifying himself as police. REUTERS/Noah Berger (UNITED STATES - Tags: CIVIL UNREST CRIME LAW TPX IMAGES OF THE DAY) 

A plainclothes policewoman searches female passengers, travelling to Nairobi, for weapons in the town of Mandera at the Kenya-Somalia border December 8, 2014. REUTERS/Goran Tomasevic (KENYA - Tags: CIVIL UNREST CRIME LAW) 

Israeli police detain a Palestinian youth following clashes after Friday prayers in the East Jerusalem neighbourhood of Wadi al-Joz October 24, 2014. Tension in Jerusalem rose on Wednesday after an Israeli baby died and eight other people were hurt when a Palestinian man slammed his car into pedestrians at a Jerusalem light railway stop. Police shot the driver as he fled. A hospital official said the driver later died of his injuries. REUTERS/Finbarr O'Reilly (JERUSALEM - Tags: POLITICS CIVIL UNREST RELIGION TPX IMAGES OF THE DAY) 

Paris airport doctor Philippe Bargain (R) demonstrates on a plain cloth policeman how airport medical staff will check the body temperature of a passenger arriving from Ebola infected zones during a press visit at the Charles de Gaulle International Airport in Roissy, near Paris October 17, 2014. France will begin screening air passengers for Ebola on Saturday if they arrive on flights from regions hit by the disease. REUTERS/Philippe Wojazer (FRANCE - Tags: DISASTER HEALTH)