Does it matter if he was trying to take the officer's gun if it is true that he was shot in the back while running away and then shot again when he turned around to surrender after being hit?
I think you could argue that the shot in the car is perfectly justified if we agree that the kid was trying to take the gun, and even the shots as he ran away if you argue for the safety of the public from a man who would try to take a cop's gun. Hard to argue with finishing the guy off after he gave up. The officer that did it is 28, I wouldn't be surprised if adrenaline just took over and that is why shooting continued after they were out of the car.