99.99% of all people (in the Western World anyway. I'm not going to speculate on the rest of the world) never shoot anybody. Because there is a certain random element to how people grow, there are always going to be some who are not well suited to life in our society. Among those is a small percentage who are going to lash out with varying degrees of effectiveness.
I don't think any kind of mass palliative educational program is going to help. A program that identified individuals who might pose a possible threat, and tracked them might help. But such a program could easily be abused, and I'm not sure we have a reliable method of identifying a dangerous person before they start shooting.
It's shitty, but as long as you've got people running around loose, shitty things are going to happen.
We could dope everyone up so they were nice obedient sheep, but even then things might not go so well. Get enough sheep going in one direction and any sheep in their way are liable to get trampled.