I can only think of one course of action that would apply in most lone-gunman mass shooting cases: EVERYONE on the scene channel the inner Super Hero, Marine, mama grizzly, Todd Beamer, or whatever amps up their kill instincts to 11, and as a group do a mass “charge the ambush!” with the express intent of taking his screw-cap off, ripping off his arm and beating him to death with the bloody stump, or stopping him in any way possible.
A primary difference, I think, between this scenario, and Flight 93, was that the folks on Flight 93 had time to communicate with their fellow passengers and coordinate a response. In the movie theater shooting, there was no time for that, which I think is the problem with collective action in a situation where there’s no time to communicate and plan. I’m certainly not going to charge an armed man and just hope some people join in. I’d need to know at least a few other people are game.
But overall, I agree with Joe with this point, “This sort of training and mindset MUST start in the schools.” Recently a friend who is a schoolteacher was up visiting, and I was relatively appalled they do regular cower and hide drills in schools these days. I offered her some advice on what to do if someone actually does get into the classroom, but if the schools are going to prepare for the extremely remote possibility of mass shootings, passivity is not what they should be teaching. Passivity will get people killed.