One other suggestion for control of violent people
Regulate and control availability of ammunition.
Tag and control sales of firing powder, bullets, clips, etc.
Make it very difficult to obtain the ammunition and weed out these lame brained perpetrators.
Just in one afternoon of practice or target shooting, one can clear 500 rounds. And a good gun owner keeps up to date with his/her skills, we don't leave them to gather dust and hope we can hit the broad side of a barn in an emergency.
2. The best, most effective, control of any person is control over themselves, no other "solution"
solves for problems with self-control without ALSO addressing WHY people are out of control and how to get as many as possible to control themselves as well as they possibly can.
Whatever other solutions people decide on, they MUST be accompanied by Mental Health parity in all health care insurance coverage, because even with the most "perfect" and just gun control imaginable, without addressing the ROOT CAUSES in human factors, the problems, in this case violence, just morph and repeat themselves in other terms.