Since we already have gun ownership requirements and registration...
1. Unrestricted gun ownership and concealed carry nationwide, in all public places. Castle Doctrine extended to your own personal space, wherever you are. If a state or locality still refuses to allow it or harasses those who abide by the law, sue them for violating your rights or move. The relatively high crime rates in those areas will speak for them in the near future.
2. Outlaw all "gun free" zones, aka Free Fire Zones/Target Rich Environments/Murder Magnets.
3. Train and require off-duty police and military to carry at all times.
4. Summary death penalty by public/televised execution for anyone found guilty by jury of murder (by any means, not just firearms). No imprisonment, no appeal...you die that same day as an example to others. Mental illness will be no excuse, and the family of any minor convicted of murder will pay all court costs and restitution to the families of all victims.
5. If it is proven you shot and wounded/killed in order to save the life of yourself or another, you get a medal and are rendered immune from pestiferous lawsuits.
Do I expect any of it to happen? Not with leftists running things and using incidents like this one to further brainwash the public to fear guns. Never happen.