"It's what happened in 2002 at the Appalachian School of Law. Hearing shots, two students went to their cars, got their guns and restrained the shooter until police arrested him.

Likewise, law professor Glen Reynolds writes, 'Pearl, Miss., school shooter Luke Woodham was stopped when the school's vice principal took a .45 from his truck and ran to the scene. In (last) February's Utah mall shooting, it was an off-duty police officer who happened to be on the scene and carrying a gun'."

Read John Stossel's column here.

Thanks, Armchair Economist.