So we agree:
Those magazines were available back then.
Semi automatic were cheaper and available.
Most guns were cheaper and easier to obtain.
School shootings were all but non existent.
Gun control laws are much tougher now.
What has changed with our society?
Well in the 60's the gun selling the gun probably would have known the kid and the whole family. And more then likely would have put keeping the gun out of the hands of a mentally unstable person ahead of profit.
Also... guns were cheaper in the 60's? huh? Not counting for inflation... or how the hell did you come up with that