Johnny Hurley, 40, was shopping in downtown Arvada, a Denver suburb, when he heard Ronald Troyke ambush and murder Officer Gordon Beesley, who was responding to a call Monday afternoon, officials said. Troyke, 59, then returned to his truck to grab an AR-15, and was holding it when Hurley — who was carrying a concealed weapon — confronted him and shot him dead, Police Chief Link Strate said in a video clip posted Friday. But when another officer responded to the scene, he saw Hurley holding the suspect’s rifle — and tragically mistook the good Samaritan for the cop killer, fatally shooting him, Strate said.