A recent phenomenon in late '90s America. Involves a rural/suburban white male teenager going to school with a serious number of semi-automatic weapons and doing the obvious. Ironically, there's been school shootings for years, but since it was minorities shooting other minorities in the inner city, it was ignored by the mass media. Of course, you're still far more likely to be beaten to death by your own parents than shot at school, but America is not known for its rationality.

School shootings are usually caused by a large number of disparate factors:
  • Violence in the media. While this is a problem, it's not of the type everyone seems to think it is. Video game violence is only a problem for those already predisposed toward violence. In other words, it will make the psychotic even more so.
  • Under-medication. In the case of Columbine, no one was making sure they were actually taking their psychoactive medication, so when they decided that the drugs took away their anger, they stop taking them.
  • Easy access to guns. Again, this is not a root cause, but rather something that compounds a pre-existing problem. That said, if your child is already taking psychoacative medication, than he/she probably doesn't need access to firearms. In fact, unless they're pretty close to being completely rational, maybe they don't need a gun anyway.
  • Bad parenting. This can actually be a root cause- bad parenting can cause an otherwise rational child to go bad, and compound the problem very quickly. Watch your kids, nuture your kid, and always remember that what you do early has a bigger impact than what you do late.
  • Exclusionary social practices in the schools. This will make certain people angry, but due its appearance later in your childhood, is generally not a primary motivating factor. While it is probably detrimental to society as a whole, any rational person can survive this.
  • Genetics. The big one. A fairly signifigant portion of your psyche is set by your genetic code. Poor genetics can be overcome by good parenting, and sometimes drugs, but poor genetics and poor parenting will really mess someone up.