Sadly, we never know who the crazies are until they do something like this. How would you propose we solve for that? Or do we just wait and clean up the mess afterward?
Does it really infringe one's freedoms to have a background check and a registration process before becoming a gun owner? Do you even give a second thought to your freedoms when your auto tags expire and you must renew them, or when you get that new driver's license? Come on now...
I am not suggesting that anyone lose their guns. I grew up hunting and have a secured handgun at home for protection. I still see no rationale for owning an AR / AK; those are weapons with one obvious purpose. Primarily I am suggesting controls on the front end. If you have a gun at home, have your registration there. If you have concealed carry, you must also carry your permit and gun registration, just like you have your drivers license and registration with your proof of insurance in the car. Simple. It is for the good of us all.
And yes, I know, the criminals will not follow the process. Caught with an unregistered gun, gun gets confiscated, you go to jail. Selling an unregistered gun, you go to jail. Common sense stuff. If the politicians had acted on this 20+ years ago as they should have, it would be a much better society today.