I have to respectfully, partially, disagree. In a crowd, you may not know who is armed. But that shooter may pull his weapon right in front of you with his back turned to you. You have a sidearm, know you are not a target, have the element of surprise, and could put that person down in short order and prevent one of those mass shootings. Of course it may not go that way. But it's just as likely that it could. I'll prepare for the chance that I could affect the outcome, before I'll prepare to be a sheep at the slaughter.
Maybe I'm different. But my family doesn't run. We haven't since WWII when my grandfather carried boxes and boxes of ammunition by hand under heavy fire to soldiers pinned down over 2 miles away. Killed several Japanese along the way. Made several trips. I could state many examples from my father, brother, and myself. But some will just claim I'm chest thumping and a armchair wannabe. And that's fine by me. Some will claim that the brave die everyday. That's true. It's a risk and a choice.
And as for the 1 of 160 mass shooting stopped by an armed citizen, they also are not taking into account how many rounds were fired BY THE ASSAILANT that MISSED. It's only based on casualties. So if they guy is a terrible shot, like the guy today, it doesn't count. Gold standard or not, it's irrelevant. Because that statistic does NOT predict how the next mass shooting will be stopped.