One, which has been disproven so often that we can only conclude that anyone still shopping it is either a deliberate liar or crazy, is that killers aiming at a big score choose "gun-free zones."
However, the Umpqua school is not free of guns. How many persons on the campus were armed is hard to say, but the number was not zero and, according to the statement linked above, was considerable. They did not ride to the sound of the guns. They sheltered in place, just like wimpy unarmed liberals.
For good reason:
“Luckily we made the choice not to get involved,” he explained. “We were quite a distance away from the building where this was happening. And we could have opened ourselves up to be potential targets ourselves, and not knowing where SWAT was, their response time, they wouldn’t know who we were. And if we had our guns ready to shoot, they could think that we were bad guys.”That is the very most optimistic view of it. Had they intervened, they'd just as likely have shot a student as a gunman, as happened in gun-happy Houston last week. Even more likely, they'd have lost the shootout with the already armed and prepped killer.
Three million Americans have been shot to death in the past century. The number who were criminals plugged by a conveniently placed gun nut is very small, and possibly (even probably) smaller than the number of innocents shot by mistake.