I agree with you that the kid shouldn't have been there with a gun, regardless if it was legally obtained or not. But I also think the protesters and rioters shouldn't have been there either. I think there was a curfew that they all violated and certainly they shouldn't have been there looting and burning businesses that had no involvement whatsoever with the police shooting, which in and of itself may have been justified under the cir stances (kind of need to wait for the evidence to come out before rushing to judgment).
I don't know that the 17 year old was a cold blooded murderer. He might have been. Or maybe he was a 17 year old that was emotional and caught up in the moment and felt threatened. I don't know. But inexperienced kids with guns should not be policing the streets. The governor should have called in the feds, but he didn't want to hand Trump a photo op, so instead he allowed this dangerous situation from all parties, including the rioters, to happen. He has as much blood on his hands as anyone.