I'm with Moshe! This child was taking a break from battle, from what they call Theocratic Warfare. In my unlegal opinion any judge in this U.S.A. would say that the boy is fair game. Moments before and after this incident he was engaged in offensive maneuvers.
Far different than if the child was at a soccer game, or hanging out at the mall, or in his front yard. In those venues I'd use more caution and discretion.
Fats