Then basically only allow rifles that take a while to reload for hunting as well as regular pistols with no accessories that can make them any more dangerous than that. Guns that take a while to reload and holds very little ammo, somebody can more easily charge and stop that person. I may not hunt, by from films I get the general impression that it's mostly a waiting game of lining up a shot so I don't see that group arguing a lot about only being allowed guns that hold few ammo rounds and takes a while to reload. At least that way, some power is at least given back to the people. You make it harder for the shooter and a lot more easier for literally anyone to stop him - there'd be fewer casualties because the odds are largely stacked against them.
I don't think it's possible to outlaw and ban completely, which I would like. But I do think it's possible to outlaw any and all guns and accessories that can easily kill a lot of people.
I should note not saying get rid of guns. Tactical teams, government operatives, military, etc. should have them - there, they serve a purpose. Regular people should not.