Surrendered handguns are piled in a bin during a gun buyback event in Los Angeles on May 31, 2014. David McNew/Getty Images hide caption

itoggle caption David McNew/Getty Images

A makeshift shrine to the victims of the school shooting in Newtown, Conn. Slate and a citizen journalist are trying to track gun deaths across the nation since that Dec. 14 mass shooting. Emmanuel Dunand /AFP/Getty Images hide caption

itoggle caption Emmanuel Dunand /AFP/Getty Images