[lutorm]

... they took place in areas where it is illegal to have a weapon in your possession. Maybe not the Giffords example...

You're right about the Giffords example. In fact, one of the attendees did have a handgun, but that did nothing to help the situation. He (wisely, one would argue) kept it in his pocket since a) he could not figure out who was shooting, and b) even if he had, he would not have been able to do anything without hitting bystanders, and c) if he had pulled the gun out, the likelihood of someone else around with a gun mistaking him for the primary shooter would leave a significant risk of him getting shot by mistake.