Well he gave up violent games years ago, so clearly it wasn't that.
Also very interesting that a kid psychotic enough that his parents had him under video surveillance (a measure found too extreme for most prisons) was still allowed access to guns... that is just brilliant, but hey some parents learn from advice, others from gun shot wounds, I imagine they might pay more attention to what the fuck they are doing with their kid now.
So do remember this lovely story for when you have some spawn of your own, if you don't do your parental work you will get shot.