Your list of school shootings makes shocking and sobering reading.
What causes school shootings? I feel their are a number of factors, all of which the MSM and Society in general fail to recognize. The primary factory being the lack of teaching proper respect of the weapon by the parents. Second would be the failure of the parents to secure the weapons properly when they are not able to supervise their child. Third would be a breakdown in the school system which tolerates improper behaviour by children and doesn't adequately respond to such behaviour. The final might be the coup de gras of the whole scenario. If proper behaviour was stressed in the school system, then those children that act improperly would have some kind of peer pressure exerted upon them, or their peers would (acting properly) rat them out. I know this works because there have been several cases in the past few years where this kind of peer monitoring has been successful. It has, in the case of the law enforcement agencies involved, averted possible disaster aking to Columbine.
Our society has become so disattached that we fail to realize the value of community. Know your neighbor. Become friends with them. And if they are not friendly, watch them that much more closely. I am not saying to be a snoop, but be wary of the unsociable because they have proven to be culprits in many crimes.