I was thinking the same thing. Full auto, and a child of this age, you would think that you would brace yourself.......and be ready to brace them.....in case anything happened. It seems like a stupid accident to me. And that's why they're called accidents.....because someone let's their guard down. Even if not intentional......they let it down no less.
Full auto weapons are extremely "fun" to play with. But there are limitations to everything...meaning the person behind the trigger. Once again......a senseless accident.