Much like the FL mob, this brings up a good opportunity to discuss stretegy in a scenario like this.
You're in a dark, packed theater when shots are fired. There's screaming and chaos with people everywhere. What do you do?
This is sad and makes me feel better about carrying the last few times I went to the movies.
Floor!!!
Next step is to activate the plan you developed when you entered the facility: Exit or cover options. Now isn't the time to worry about them. You thought about it, and now you do what options are left based on where the shooter is. According to current accounts he was in the screen area, so the doors you entered through may be the best route.
By the way, if you are able to flee through an exit the firearm should be holstered but accessible and light in hand. If you are trapped inside firearm and light in hand and ready if needed.
Hit the floor and stay there, under the seats if possible, the exits will be jammed and provide choke points for a shooter to concentrate on. If he approaches you and targets you, then attack him, throw your soda in his face, hit, kick, bite, talk about his mother, what ever it takes to protect you and yours.
This is a much different situation than the "flash mob". they were looters, focused on stealing stuff from the store and vandalism, getting out of the area is the best tactic, if you are seen moving away you are obviously not interfering with their actions, therefore you are of minimal interest to the mob.
A mass shooter has a different agenda, he is looking to wrack up numbers, his attention will be focused on "target rich" areas, such as exits, and movement that draws the eye will likely draw fire that could have otherwise been avoided.