How to explain the likes of "Machine Gun Kelly", "Pretty Boy" Floyd, and of course "Bonnie and Clyde". Big "gun violence" types, who lived and died before 1963.
These people were criminally mentally ill. Or are you going to argue that they were, somehow, "sane"? Prohibition was the social vehicle through which they could be violent and the depression the reason that their were too few mental institutions. Actually, mental hospitals are the province of the rich and crazy, violent lifestyles the province of the poor and crazy. World War II put most of the violent men of the 1940's in the army. Right now, the prisons are full of their types who should be in mental hospitals. Permanently.