EDIT: Changed the title, primarily because I didn't talk specifically about the Aurora scenario.
I don't want to get political with this post, and I don't intend to start a discussion about what people should have done. The killings in Aurora, Colorado were senseless violence, perpetrated by someone who intended to kill as many people as he could. In the face of such a person, there is little that can be done except to kill the attacker as soon as possible in order to stop bystanders from being killed.
Unfortunately, this will not be the last time that someone assaults a crowded space with the intent of causing death and grievous bodily injury. As long as there are weapons, and evil people who can get their hands on weapons, they will want to hurt as many people as they can. However, the flip side of that, as Col. Jeff Cooper noted, as long as there are good people with weapons, they can thwart the evil ones.
What I intend to do is simply discuss different tactics, techniques, and procedures for thwarting someone, should an attack come to a theater, shopping mall, or college campus while you are there. There is always something that can be done in an active shooter situation, rather than cowering on the ground, hoping the shooter won't see you and your family. Sometimes the answer is to seek a covered and concealed route away from the shooter. Other times, the answer is to find the quickest way to attack the shooter. It is very much situational, as self-defense expert, military and police veteran Hock Hocheim says.
I'm going to go in the order of most probable scenario, to most dangerous scenario, just as if I were briefing a group of soldiers. I will leave it up to you, the reader, to flesh out the scenarios in the middle. Most probable means simply that, what is the situation you are most likely to find yourself in. Most dangerous is the scenario that is most likely to end with you and your buddies being wounded or killed. I will go in order of pistol, knife, impact weapon, improvised weapons, and unarmed.
First the pistol. Most probably scenario is that you are in a crowded place, and hear shots popping off. Take cover, assess the situation. You will see this again. Most likely you will be able to tell if it is actually gunfire. If so, find a covered and concealed route away from the gunman, if you do not have a visual on him. The reason that I say to not draw the pistol first is that in the immediate aftermath of the first few rounds going off, people are not going to be real clear on who the bad guys or good guys are. Everyone with a firearm is automatically going to be put into the bad guy category. Get everyone calm first, work out a plan to get away from the shooter, and then explain that you have a pistol and are going to do your best to get everyone to safety. Where you position yourself in relation to the people you are trying to help depends on your preference, and the terrain. Me being me, with my combat and firearms experience, if police haven't arrived yet, depending on the building, I would probably go back into the building and see if I can get anyone else out, or locate the shooter. I don't recommend that for everyone, as it's very easy to add to the confusion. If it was a small building like a Burger King, I would probably continue to make sure everyone is safe and stay out of the way of first responders.
The most dangerous scenario is that you find yourself face-to-face with the shooter. The instinctive response is to run, but recognize that his weapon will become more effective as you open up the range, and not less. Once you get inside the range of a firearm, their effectiveness diminishes. Thus, grab the gun, charge the bad guy, and be prepared to beat the snot out of them. From medium range, between 5 and 30 feet, throw something at the bad guy's face, charge, and beat the snot out of them. Beyond 30 feet, you will need to take cover and then draw your primary weapon in order to successfully defend yourself with your own firearm. The best thing to do would be to draw while moving to cover, but this may not always be possible. If there is no cover available, then the next best option is kneeling, in my opinion, in order to minimize your target profile.
This post is long overdue, so I will simply say to be continued.