They only ran off after he drew the gun. That means before he pulled out his gun, they were still beating him. Letting them run off was a dereliction of duty. If some people break into your house, assault your wife and children, but start running when they see you entering the room with your pump shotgun, would you just let them run off?
Would you shoot someone in the back who is running away?
That’s the hallmark of a coward, isn’t it?