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Personally I think there is a link in A-moral violent video games as well as violent music that glorifies killing. Now in saying that please don't construe it with me being an advocate for censorship. I am not, but I think there is a link.
Further if you couple that with young males who have little prospects in this brave new world, fresh out of school or getting ready to graduate, no real direction and probably a hand full of romantic rejections due to being awkward you have a powder keg waiting to happen.
Funny enough in the case of the Texas shooter, after reading his manifesto, I was surprised he did not use explosives. His reasoning where more like Timothy Mcveigh's than many of the other shooters. He does not fit the typical profile.