He sounds like one of those that usually having a mental disease or behavior problem that often leads to being easily angered with high levels of rage. Usually a take down and a few hours in a secluded room with an IM will temporarily take care of the problem. These patients typically have NO impulse control. Just the type the mental hospitals were originally designed to treat or house. I can't believe he wasn't on some type of legal medication.
The medical induced 3 day coma tells me he was probably on a respirator for three days after the event.
Think about it, the staff could not handle the kid, they HAD to call the police and the trained professionals could not cope with the violence.
I'm sorry if the kid was born with this problem, but if someone has to die, better this violent kid dies before killing another some other time in his life.