The main two things I keep hearing about this one are, he was practically stalking some girl for weeks and she finally embarrassed him in class to make him stop, and also, that the football players and coaches picked on him all the time.
So again... why are these kids nowadays so f*cking brittle that some of the most common and benign disappointments life will ever throw their way put them right into a "Kill Everyone" mindset? Yeah, that's rational.
It's almost like they have no idea how to cope with things not going their way.
This is what happens when you lie to kids and tell them every feeling they ever have is "valid" and they'll get everything they ever want as long as they "just keep trying" (which in their minds will read, "Stalk and harass a girl until she gives in," for example).
Maybe we ought'a start toughening 'em up way earlier in life by telling them the truth: MOST things in life aren't going to go your way, you CAN'T get everything you want in life, MOST things are beyond your control, MOST of your dreams won't come true, MOST people aren't going to like you, NO, they don't need a reason, NO, you won't change their minds, and YES, you're going to be judged more for your looks, money, and social status than anything you ever do as a human being. If being a "Good Person" or making a "Contribution to Society" meant anything at all, doctors would make more money than football players, but they don't and never will. ALL LIFE is about "Injustice", disappointment, and how you react to it defines who you are as a person. The measure of a human being is not how they act in victory, but in defeat. And so on.
All of that was made perfectly clear to me before like, Age 5. Yes, I grew up cynical, bitter, and kinda mean, BUT I also became so familiar with disappointment that I've come to expect it, and thus am far better emotionally-prepared to react to it. It's almost better to just expect things to go wrong, and be pleasantly surprised when they go right, than to expect everything to go your way and be completely unprepared to handle it when it doesn't.
I mean, you don't have to be mean about it, just be honest with kids. Maybe if they grow up NOT expecting to get everything they want and ask for, they won't start shooting people when they don't get it. Seems like a way to go. It certainly hasn't been tried in a long time.