50 years ago?
These shootings are happening within the last 2 plus decades.
And that's when the gun manufacturers started dropping tons of guns on the populace.
when they realized that nutty people were their best market, because they can't stop at just one.
While the number of households with guns in them declined, the number of guns out there increased.
Just like the alcohol industry realized that drunks were there best customers, the gun industry realized their best customers were insecure white males with anger issues....
Mass shootings aren't a bug, they're a design feature of that plan.