Last June in Arvada, Colorado, a man who said he wanted to kill police officers ambushed and killed one. He was in turn immediately shot and killed by John Hurley, a 40-year-old bystander who was lawfully carrying a concealed pistol. Hurley then picked up the dead man's rifle. Unfortunately for him, another policeman responding to the sound of gunfire took a quick look at the situation, mistook Hurley for the original gunman, and shot him dead. The whole incident took two minutes. Now the local prosecutor, after an investigation that included surveillance video of these events, has concluded that the second officer made an honest mistake in an emergency and should not be prosecuted. So much for the belief that an armed citizenry will promote public order.