Mass Killings - How (other than some 2nd Amendment Issue) Can we Stop Them?

Just curious what might be a good place to start an intelligent (not hate filled), conversation on this issue. We all know our elected folks can't seem to do it, so let's hear what you think. What are the causes, how do we deal with the causes? Obviously we can't eliminate them entirely, but how can we lessen the frequency... This IS NOT a political discussion - all hateful comments will be deleted.