FWIW, I disagree. There have been bullies since well before Eddie Haskell. Some people are simply evil. This guy is one of them.
Plenty of people knew this guy was dangerous, both to himself and to others, for a long time before he went on this rampage and none of them did anything about it.
Having 'gun free zones' is like announcing to psychopaths where the best hunting grounds are.
EDIT: Mentioning that some how bullying in even some small way helped turn him into a psycho shifts some of the blame from him to 'society'. How can 'society' be so cruel, etc. Time was people like this, who had been diagnosed with problems since high school, would have been involuntarily committed. Not these days. No, 'society' can not do anything to either help these people nor protect the rest of us from these people. We must protect their civil rights. If someone had tried to have him committed they would have been slapped with a lawsuit so quick it'd make your head spin. No, these days we must wait until they do something like this, then we wonder what happened and why. Or worse yet, blame it on lax gun laws. If the gun laws were only stricter, who needs pistols anyway, etc. One of the things I've learned working in IT is, if you don't fix the root cause of the problem, it will happen again. Better yet, play the rants and ravings of a psycho over and over again on national TV, it's 'news' don't you know, and see how many other fuses of psychos you can light.