One issue often overlooked here is also the media. Each killing gets covered more and more in-depth. Each shooter becomes more and more a household name. This just leads to more shootings.
But how do you stop that?
We don't know. It's not an easy thing to change. Of course the networks won't stop covering - it's huge ratings. The government doesn't have a leg to stand on to stopping them. And people just tune in.
So there's really nothing we can control there, and that's probably the single biggest factor in why this happens - people wanting to be famous.
Ultimately we can't stop these. All we can do is lessen their frequency and their damage. Hence: smaller clips. Hence: more restrictions on getting guns.