Just a quick thought on our latest mass shooting:
This kind of thing is not going to go away until some of the basic features of our culture change. Probably central to that would be a weakening of our cult of extreme individualism, which is reproduced every generation via the mode of socialization known as independence training. Independence training reduces personal responsibility to the larger society, and also reduces empathy. It helps us remain a nation suffering from culturally-induced psychopathy.
The strength of this cultural feature varies through time, as it does also across social and geographical space, but it's always there.The "Reagan Revolution," as well as Trump's "Make America Great Again," were/are revitalization movements for this cult.