U.S. Secretary of State Rex Tillerson visits the Nahuel Huapi National Park in Patagonia during his Latin America tour, in Bariloche, Argentina February 3, 2018. REUTERS/Osvaldo Peralta

U.S. Secretary of State Rex Tillerson visits the Nahuel Huapi National Park in Patagonia during his Latin America tour, in Bariloche, Argentina February 3, 2018. REUTERS/Osvaldo Peralta

U.S. Secretary of State Rex Tillerson visits the Nahuel Huapi National Park in Patagonia during his Latin America tour, in Bariloche, Argentina February 3, 2018. REUTERS/Osvaldo Peralta

U.S. Secretary of State Rex Tillerson visits the Nahuel Huapi National Park in Patagonia during his Latin America tour, in Bariloche, Argentina February 3, 2018. REUTERS/Osvaldo Peralta

U.S. Secretary of State Rex Tillerson visits the Nahuel Huapi National Park in Patagonia during his Latin America tour, in Bariloche, Argentina February 3, 2018. REUTERS/Osvaldo Peralta

A man lights candles next to a portrait of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, placed at the entrance of a judicial morgue in Buenos Aires, Argentina October 20, 2017. Picture taken October 20, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, shows a tattoo with a portrait of his brother during a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, shows a tattoo with a portrait of his brother as he speaks during a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, shows a tattoo with a portrait of his brother as he as he speaks during a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, speaks during a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Sergio Maldonado, brother of young protester Santiago Maldonado, who went missing when security forces clashed with indigenous activists in Patagonia on August 1, 2017 and was found dead in a river on October 18, shows a tattoo with a portrait of his brother as he arrives for a news conference at Amnesty International headquarters in Buenos Aires, Argentina October 27, 2017. REUTERS/Marcos Brindicci

Portraits of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, are seen at the entrance of the polling station where Maldonado was registered to vote in his hometown of 25 de Mayo, Argentina October 22, 2017. REUTERS/Jorge Otaola

Portraits of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, are seen placed on trees in a park in Maldonado's hometown of 25 de Mayo, Argentina October 21, 2017. REUTERS/Jorge Otaola

A woman walks past a graffiti with an image of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, in Maldonado's hometown of 25 de Mayo, Argentina October 21, 2017. REUTERS/Jorge Otaola

A woman walks past election campaigns advertising posters of the Left Front party with images of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, in Buenos Aires, Argentina October 21, 2017. REUTERS/Marcos Brindicci

A man lights candles next to a portrait of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, placed at the entrance of a judicial morgue in Buenos Aires, Argentina October 20, 2017. REUTERS/Marcos Brindicci

A man lights candles next to a portrait of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, placed at the entrance of a judicial morgue in Buenos Aires, Argentina October 20, 2017. REUTERS/Marcos Brindicci

A woman holds up a sign refering to Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, during a demonstration outside a judicial morgue in Buenos Aires, Argentina October 20, 2017. The sign reads "Santiago, you live among us". REUTERS/Marcos Brindicci

A woman touches a portrait of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, placed at the entrance of a judicial morgue in Buenos Aires, Argentina October 20, 2017. REUTERS/Marcos Brindicci

A man walks his dog past a portrait of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, placed at the entrance of a judicial morgue in Buenos Aires, Argentina October 20, 2017. REUTERS/Marcos Brindicci

A woman places flowers next to a portrait of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, at the entrance of a judicial morgue in Buenos Aires, Argentina October 20, 2017. REUTERS/Marcos Brindicci

A man sits next to a portrait of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, at the entrance of a judicial morgue in Buenos Aires, Argentina October 20, 2017. REUTERS/Marcos Brindicci

A man sits next to a portrait of Santiago Maldonado, a protester who went missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, at the entrance of a judicial morgue in Buenos Aires, Argentina October 20, 2017. REUTERS/Marcos Brindicci

A man wearing an Argentine flag over his body talks to a man who wears a t-shirt with an image of former Argentine First Lady Eva Peron during a demonstration to demand information about the disappearance of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, outside the Casa Rosada Presidential Palace in Buenos Aires, Argentina October 19, 2017. REUTERS/Marcos Brindicci

People display signs with portraits of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, during a demonstration in Buenos Aires, Argentina October 19, 2017. REUTERS/Marcos Brindicci

A man holds up a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, as he marches alongside members of the human rights group Madres de Plaza de Mayo (Mothers of the Disappeared) during a demonstration in Buenos Aires, Argentina October 19, 2017. Words on the portrait read "Where is Santiago Maldonado?". REUTERS/Marcos Brindicci

A man shouts slogans as he shows a a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, during a demonstration in Buenos Aires, Argentina October 19, 2017. REUTERS/Marcos Brindicci

A woman and a child show portraits of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, during a demonstration in Buenos Aires, Argentina October 19, 2017. REUTERS/Marcos Brindicci

A portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, is seen below the Piramide de Mayo (May Pyramid), in front of the Casa Rosada Presidential Palace, during a demonstration in Buenos Aires, Argentina October 19, 2017. REUTERS/Marcos Brindicci

People hold images of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, during a demonstration to demand information about his disappearance in Buenos Aires, Argentina October 18, 2017. Words on the sign (L) read "Where is he?". REUTERS/Marcos Brindicci

People hold portraits of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, during a demonstration to demand information about his disappearance in Buenos Aires, Argentina October 18, 2017. REUTERS/Marcos Brindicci

A woman holds up a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, in front of the Casa Rosada Presidential Palace during a demonstration to demand information about his disappearance in Buenos Aires, Argentina October 18, 2017. REUTERS/Marcos Brindicci

A man holds up an image depicting Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, in front of the Casa Rosada Presidential Palace during a demonstration to demand information about his disappearance in Buenos Aires, Argentina October 18, 2017. The words on the sign, below the image, read "Where is he?". REUTERS/Marcos Brindicci

A man looks at his cell phone in front of a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia on August 1, 2017, at a demonstration to demand actions to find him, in Buenos Aires, Argentina September 1, 2017. Words on the banner read "Where is he?". Picture taken September 1, 2017. REUTERS/Marcos Brindicci

People walk past images of Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia, during a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Maldonado and Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes. The words on top read "Where is Santiago Maldonado?" REUTERS/Marcos Brindicci

A man holds up a sigh that reads "Never again" during a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes, and Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia. REUTERS/Marcos Brindicci

A man holds up an image of Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia, during a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Maldonado and Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes. REUTERS/Marcos Brindicci

A man holds a sigh that reads "Never again" as he and a woman show images of Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia, during a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Maldonado and Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes. REUTERS/Marcos Brindicci

People hold a banner with an image of Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia, during a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Maldonado and Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes. REUTERS/Marcos Brindicci

A woman reads a newspaper as she shows a sign with an image of Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia, before a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Maldonado and Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes. The sign reads "Where is Santiago?" REUTERS/Marcos Brindicci

A man wears a t-shirt with an image of Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia, during a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Maldonado and Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes. The t-shirt reads: "Where is Santiago?" REUTERS/Marcos Brindicci

Nora Cortinaz (C), the leader of the human rights group Madres de Plaza de Mayo (Mothers of the Disappeared), and other members of the organization march during a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes, and Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia. REUTERS/Marcos Brindicci

People hold a banner that reads "Julio Lopez, 11 years" as they march during a demonstration in Buenos Aires, Argentina September 18, 2017, against the disappearances of Julio Lopez, who disappeared 11 years ago before testifying against dictatorship-era crimes, and Santiago Maldonado, who disappeared on August 1, 2017 after taking part in a protest in Patagonia. REUTERS/Marcos Brindicci

A street vendor sells sausages during a demonstration to demand actions to find Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

A street vendor grills sausages during a demonstration to demand actions to find Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

A man holds up a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, during a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

A man wears a sign over his forehead with an image of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, during a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. The words on the sign read "Appearance alive, now!". REUTERS/Marcos Brindicci

A woman holds a sign with a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, during a demonstration to demand actions to find him in front of the Casa Rosada Presidential Palace in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

A protester throws stones at the police as he sits over a police fence in front of the Casa Rosada Presidential Palace during a demonstration to demand actions to find Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

A protester sits over a police fence in front of the Casa Rosada Presidential Palace during a demonstration to demand actions to find Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

Protesters throw stones at the police as others hit a police fence outside the Casa Rosada Presidential Palace during a demonstration to demand actions to find Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

Children play on the street over drawings with the words "Where is Santiago Maldonado?", during a demonstration to demand actions to find Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, in front of the Casa Rosada Presidential Palace in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

Taty Almeida, a member of the human rights group Madres de Plaza de Mayo (Mothers of the Disappeared), holds a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, as she arrives to a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

A man waves an Argentine national flag next to a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, during a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. The words on the sign read, "Avellaneda (city) demands his appearance alive, now!". REUTERS/Marcos Brindicci

A man waves an Argentine national flag next to a sign with a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, during a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. The words on the sign read, "Avellaneda (city) demands his appearance alive, now!". REUTERS/Marcos Brindicci

A girl holds a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, during a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. The words on the sign read, "They took him alive, we want him back alive". REUTERS/Marcos Brindicci

A member of the human rights group Madres de Plaza de Mayo (Mothers of the Disappeared) holds a portrait of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, as she arrives to a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

People hold up signs with portraits of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, during a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

People holds up portraits of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia one month ago, during a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci

An image of Santiago Maldonado, a protester who has been missing since security forces clashed with indigenous activists in Patagonia, is seen on a screen during a demonstration to demand actions to find him in Buenos Aires, Argentina September 1, 2017. REUTERS/Marcos Brindicci