What to do when a mad gunman shows up?

This article was printed in Slate after the Virginia Tech shootings. It assumes you don't have a firearm yourself, which in no way am I advocating.

To disarm a gunman, you'll need to take his focus off his weapon and his plan of attack. To do this, you might throw chairs, laptops, or fire extinguishers at him, or set off the sprinkler system or fire alarm. Then, you'd want to pick up a desk or some other shield and charge right at the killer. There's a chance you'll be killed in the process, but if two or three people rush at once, there's also a chance that somebody will take him down. (Unarmed civilians who band together have a much better chance of surviving an attack.)

If you're already within a step or two of the gunman, you might be able to grab his weapon. If he's facing you, quickly reach up and take hold of the barrel, and then aim it away from your body. The move should be as clean and economical as possible. The gunman will reflexively pull the gun back away from you. Go with him: Keep gripping the gun and push your weight forward. Then, punch him in the face or the throat as hard as you can. Hit him on the nose, jab your fingers into his eyes, or strike him with the heel of your open palm. Then use your free hand to grab the nonbusiness end of the gun. With two hands on the gun, you can knee the killer in the groin or head-butt him. A better idea might be to twist your hands like they are revving a motorcycle engine. The weapon will pivot and break the gunman's finger inside the trigger guard.