FILE This July 20, 2012 file photo shows police outside of a Century 16 movie theatre in Aurora, Colo. after a shooting during the showing of a movie. Frightening episodes of gun violence have been splayed across front pages with alarming frequency this campaign season: The movie theater killings in Colorado, the Sikh temple shootings in Wisconsin, the gun battle outside the Empire State Building, and more. Guns are used in two-thirds of homicides, according to the FBI. But the murder rate is less than half what it was two decades ago. (AP Photo/Ed Andrieski, File)