There is another solution, besides executing "gun criminals" or total banning of firearms, but it is also unacceptable to the public in general.
That "solution" would be a simple complete "hands off" by the legal system of the people who SHOOT BACK!
It would be messy, it would be, for a time, bloody, and yes many innocent people would suffer (but aren't they suffering today??)
But consider this, that over time, if it were allowed (let alone encouraged) bad guys would learn that if they went out shooting people for fun or profit, someone would shoot them. Not try and arrest them, just shoot them dead. Maybe shoot them in the back, or from cover, or...?? Maybe multiple someones would shoot them....
And THEN call the police to "police up the body"...
It would be bad, nd the streets would run with blood...for a time
AFTER that, I think we'd see a lot less of gun violence or any other kind.
Can't do it today, but it did work in the past, and there's even evidence it would work today, if we, as a people, were willing to pay the cost.
Consider that the majority of the killers are not willing or interested in doing their killing where people are armed and could shoot back. (death seeking jihadiists are a different matter)
After Florida passed its "shall issue" carry permit laws, there was an interesting change in the crime rate. Crimes against Florida residents decreased, crimes against tourists went up. Seems the bad guys were watching people's license plates and could be sure that out of state plates meant the people were unlikely to be armed, while Florida plates meant they couldn't be sure...
These people, overwhelmingly target people they believe cannot defend themselves. If we change that, we change everything.