I'm all for it. Where do you begin ?
Banning firearms and having strict policies to hand in your weapons ? As I posted earlier. Good luck with that.
Here are some places you can begin.
Start with a buy back option to get numbers down. Legal or illegal.
Put in place stricter background checks. This guys dad was a wanted felon, maybe there should be some sort of list that limits and tracks the amount and type of guns the kids of felons buy. (granted, I can see constitutional issues with this one)
Ban private sales.
Increase training requirements.
Mandatory safety classes every few years.
Allow home inspections to see how your gun(s) are stored.
Limit clip size.
Encourage recreational users to keep their guns at the range or club rather than at home.
and one fairly radical idea, gun insurance. You can't own a gun (or 10) without paying a monthly insurance premium.
Sure, a lot of these ideas wouldn't have stopped this guy but it's about changing the mindset, it'll take time but it'll never happen if we don't start somewhere.