Why do you think we've been having a lot of school shooting and stuff?
theres so much pressure but on kids about high school. to the point where these kids are told that if they dont succed in high school then their doomed to fail at life. that is so destrutive to someone thats not considered normal or the in crowd.
People get bullied and such and can't handle it, so they defend themselves the only way they can think of while under massive amounts of pressure that's put on them by their peers.
Evil influences in the shooter's lives and poor up-bringing, lack of respect / values.
Cause some people get bullies, stressed, or fed up with the world. ..or crazy.