I believe he knew exactly what he was doing, but his brain could no longer differentiate between acceptable social interaction and senseless violence. I also believe, but we may never know due to confidentiality laws, that this kid was pumped full of psychoactive drugs for much of his life. That's not making an excuse for him, but a statement that our ability to properly address mental health issues is almost non-existent. We have allowed Big Pharma to take over the responsibility for "fixing" our children, much to our detriment. The increased rate of incidence coincides with an increase in "new" treatment, and that's not a coincidence.
The alternative is to question and research on your own everything your doctor tels you, and every medication they prescribe. My kid was having anxiety attacks, went on a couple of months, we took her in, the doctor said all tests were fine but then said she should start taking "xyz" pills. We opted to hold off on tht idea to do our own research, asked for literature from the doctor, and left.
A few days later I'm having lunch with my kid and we're talking about her hectic schedule with school, softball, volunteering, a social life, etc etc. part of her routine was to meet classmates at a Coffee Bean after school to group study, then come home and eat, chill a bit, then study until hitting the rack, sometimes well past midnight. Then up again at 530 to do it all over again. I asked her what she had to drink at Coffee Bean, and if she was tired in the morning did she stop in for something to "pick her up" on the way to school. Turns out she was wired most all day and into the night and dead tired and stressed by the time she fell asleep.
I suggested she back off on Coffee Bean for a while.
Anxiety gone. That simple. No pills.
F you very much, "health care."
Don't medicate your kids, talk to them. Accept your personal responsibility as a parent. Rant over, happy ending.

Ladies, if a man tells you he will fix it, he will fix it. There is no reason to remind him about it every six months.