He was with several adults, pervert.
He wasn’t.
Yes he was. Later, he gets separated from them while fleeing an angry mob.
But that is not actually relevant. Possessing an illegal weapon or even firing it does not mean you are guilty of murder - that is a different charge. The videos of the incident blatantly show a mob running him down and then trying to assault him. After slamming him in the back of the head he falls to the ground then turns and fires on those assaulting him.
He may be guilty of several crimes or he may not. The footage is not totally clear there. It really is no surprise crap like this happens when you pull the cops back, refuse to actually protect people from violent mobs and then make demands that people cannot protect themselves either. I am not sure what you expected - people to just lie down and let their property be smashed, burned and looted? To allow violent mobs to kill them?
You have to be a special kind of stupid to chase down and assault someone fleeing with a rifle.
He should not have been there, it was a moronic decision for him to go there even if he did so with good intent and he is going to pay for that. Guilty of murder though - not a chance.