Fine, you can have all the guns you can eat because our stupid court system has completely ignored the part of the Constitution which conditions bearing arms on membership in a "well regulated militia". However, where does the Constitution say you can sell weapons? Where does it say you can buy them from any dodgy hillbilly at a flea market?
It is time to eliminate the sale and trade of firearms between private individuals. You can buy as many guns as you wish, but only from a licensed dealer operating within your own state with a physical establishment. They must conduct full background checks and keep accurate records which are audited annually. Sell a weapon to a single ineligible person and your are out of business. Records must be kept on the sale of weapons, ammunition, high capacity clips any and kits which allow modification of a firearm from its factory specs. Mail order sale of guns, ammunition and accessories is banned.
Also, isn't it time we paid attention to the militia requirement? If you wish to own firearms, then you need to belong to a county militia which checks you out just like you were joining the army. You will require the same amount of training in the use of firearms that police and soldiers must endure and be qualified every year to ensure that you have no criminal infractions and are mentally competent to handle and properly use a firearm if needed.
Automatic disqualifiers for firearms ownership are:
1) Any crime involving violence and/or the threat of violence, especially domestic abuse.
2) Any crime involving the improper handling of a firearm.
3) Any crime involving the improper sale of a firearm.
5) Drug crimes involving any drug except marijuana.
Update: The use of a firearm in the commission of a crime must be punished harshly, especially if someone is harmed.
Also, while the first part of my proposal would not have helped in the current mass murder, it would certainly affect the 15,000 plus annual gun deaths in this country.