I'm sure we'd all like to think we could be in a situation like this and save the day with our CCW, but a crowded theater?
If I was there, I would likely be looking for cover versus trying to save the day. I might have my hand on or near my pistol in case the nut job gets close to where I was, but taking a shot at him form wherever? If it was as crowded as the stories indicate, you'd have just as good a chance of hitting a panicking movie-goer that ran into your line of fire just as you pulled the trigger as you would hitting the nut job. Even if you drew when he approached close to you, with panicking people surrounding you within touching distance, again, it would be hard to get a shot off, and there's the chance someone mistakes you for another bad guy and you get piled on by other people trying to save the day, or piled on by a mob running for the exit.
If I were in a secure shooting position with a clean shot, maybe I'd try to save the day. Otherwise, duck and cover, and if it looks like you or your loved ones are next in line, do what you need to do and take your chances I guess. From the description of the shooting scene so far, it's hard for me to come up with some kind of action hero, save the day response.
This is probably why I like to avoid crowded places.