What is needed is ammunition and access control. This is what I propose.
Control who can access weapons through strict licensing procedures. If we can conduct driving tests and written tests to assess knowledge before issuing a DL, we can do the same for firearms licenses too. Require them to take professional classes/courses in firearm safety/shooting before qualifying to apply for a license. Make sure each person applying for a license is also given a thorough psychiatric evaluation.
Control how much of what type of ammunition someone possesses. No open or conceal carry. You can possess certain calibres and certain quantity of said calibres at home for home defence. No self reloading. You only get to shoot other calibres (like the AK47 bullets), at firing ranges - make it possible to buy those bullets in whatever quantity at the firing ranges, but people cant leave with leftovers - they need to be turned in. You should not be able to bring in bullets of any kind, rather you need to purchase all bullets at the firing range and use them up (or return them for a refund at the firing range). If you own a ranch, you cannot convert a part of it into a firing range. No public sales of regulated ammunition types in stores and even with ammunition that is allowed, only a certain quantity can be purchased at one time, which will be tracked through your license as you will be required to scan it at any store you buy them and once you buy ammunition, you cannot buy more unless you provide proof of use, through a police report.
I think with controlling ammunition, who has access to guns, where they get to use it, you can bring gun related violence down. I mean a mass shooter maybe be ale to legally procure a weapon but not the bullets to use them.