You should ban weapons first, and then try the more liberal perspective.
If he was armed with a gun, ok I understand that he is shot. It's practically self-defense with a man with a weapon in your house. But if he wasn't, the punishment he now has far outweighs the crime he comitted.
Why the hell do you need weapons anyway in stores? Against criminals, bad goverment, for shooting ranges? Sounds pretty stupid to me, but then again, I come from the netherlands and we are generally very liberal. I don't understand the whole gun thing in america.