As a victim of bullying myself, this kind of stuff makes me furious. In high school, I was bullied so much that I became socially isolated and highly paranoid. It took years to undo the damage and when they were finally confronted over what they were doing, my bullies claimed they were "just having some fun." Had things gone slightly differently for me one way or another, I could easily have been one of those kids who snapped and shot up his school or who committed suicide as a way to "escape" what seemed like an otherwise inescapable situation.
As far as I'm concerned, every kid who bullied her and every adult who turned the other way has blood on their hands.