The NRA plays a big role in this as well. They don't simply or mainly represent the interests of the "gun lobby." Last summer, the NRA released a "recruitment" video that was a barely disguised call to arms to its five million members and to fascist ground troops more broadly. When there was an uproar over the video, the NRA doubled down with a second video attacking some of its critics by name. Such mobilization of white supremacist, America-Number-One, fascist forces is deadly serious--and must be taken very seriously. Just a few months before this, Trump had appeared at the NRA's national meeting and declared, "You have a true friend and champion in the White House."
It's not because they need the votes or campaign contributions, but because they aim to keep weapons directly in the hands of their racist, white supremacist social base.
Coursing through all this are the economic and social relations of capitalism. This is a system driven by ruthless competition for supremacy and maximum returns. It's a system that promotes the dog-eat-dog outlook of "looking out for number one." It forces people to be selfish and compete with others for grades, for jobs, for housing, for partners and relationships, in every facet of their lives.
These relations, this ethos, and this wanton culture of gun violence are relentlessly celebrated and promoted in American culture from violent video games like "Grand Theft Auto," to countless TV shows and movies where the payoff is individual vengeance.
In short, a number of factors drive the massive distribution of high-powered guns and the use of some of those guns in seemingly random massacres. The point is not that every mass killer, or even most, consciously acts out a political agenda (though some do). But the economic and production relations of a society, and the dominant ideas that flow from them, do set the stage on which people act. In that sense American society and culture is guilty as hell.
(Note: You can view every article as one long page if you sign up as an Advocate Member, or higher).