A police officers puts a surrendered shotgun inside a plastic bin during a gun buyback event at Los Angeles Sports Arena in Los Angeles, California May 31, 2014. The event was announced by Los Angeles Mayor Eric Garcetti after last week's killing spree at the University of California, Santa Barbara that left six students and the shooter dead. REUTERS/Kevork Djansezian (UNITED STATES - Tags: SOCIETY CRIME LAW)