It's primarily because of psychological factors that are ultimately the result of philosophic ideas that argue against the efficacy of human reason and against the validity of the senses and the fact of an objective reality. People affected by these malevolent ideas, (which is almost everyone), develop an attenuated grasp of consequences. After all, if nothing is real, if we are in a simulation, if we are on the verge of extinction due to (fill in the blank - currently global warming), if as an American we are "the bad guys", then hope is replaced by nihilism. A person so affected can think, "what does it matter what I do, if it feels like "justified revenge" to me?" This is the root cause.

Oh, do you think philosophical ideas don't matter that much? Of course you do. This is the way someone already well along the road to nihilistic despair regards ideas.

This phenomenon is world-wide. Look at knife crime statistics in countries where there are far fewer guns. Look at bombings. Look at suicides. All guns do is provide a simpler, easier path for the expression of such feelings. Take all the guns away and we'd have far more violent crimes using different weapons. Mass killers would have to get more creative. This could easily be worse than what might have been done with a gun.

I sincerely wish we could just remove all guns for a couple of years. Then we'd be able to get over this misleading claim that guns cause these crimes. It's the glorification of the irrational and the condemnation of the human in our news and entertainment media, (movies such as 'Kill Bill' and 'Avatar' and hundreds like them for example). It's the demonization of 'selfish' ambition we teach our kids via our public education system. Its these prevailing philosophic ideas that are most fundamentally responsible. Guns just make the killing easier. They do not cause the killing. Ideas cause the killing.