EAST DUBLIN, Ga. — Video from a police cruiser in rural Georgia town shows just how quickly a traffic stop can turn deadly.

In the recording, officer Jeffrey Deal jumps out of his patrol car and runs toward Melvin Williams, who has gotten out of his vehicle. The two begin fighting. Williams punches the officer in the head and takes a couple of steps toward Deal, who draws his gun and fires, killing the unarmed Williams.

Police encounter similar split-second decisions each day and rely on their intensive training and “shoot or don’t shoot” scenarios to guide them. Yet in this case, Deal had gone more than a year without a mandatory training on the use of deadly force. He should have lost his arrest powers several months before the May 2010 shooting, according to a report from state investigators.