But, once again, there was an armed citizen on the scene as The Record-Courier (Gardnerville, NV) mentioned:
Ralph Swagler, owner of the adjacent Locals BBQ restaurant, told the Nevada Appeal that he saw the gunman pull up in a minivan, get out and begin firing an automatic rifle at the IHOP. The gunman then reloaded and went inside, and Swagler said he heard more gunshots inside the restaurant...Not that I totally blame him for erring on the side of caution given that he was outgunned.
Swagler said he had a handgun and considered opening fire on the shooter, but he didn't want to engage a gunman who was armed with a fully automatic weapon.
Early in the Columbine shootings, a Jefferson County deputy sheriff arrived at the scene and began shooting at Harris and Klebold, distracting them from the injured Brian Anderson. Anderson staggered out of the area and made it into the library, where he ran into an open staff break room. He remained there until the ordeal ended. Harris fired ten shots at the officer, who then radioed in a Code 33 (officer in need of emergency assistance). The shooting continued for another 18 minutes.
When Gabrielle Giffords was shot, Joe Zamudio almost shot the wrong person. The Arizona Daily Star added two details to the story based on its interview with Zamudio First, upon seeing the man with the gun, Zamudio "grabbed his arm and shoved him into a wall" before realizing he wasn't the shooter. And second, one reason why Zamudio didn't pull out his own weapon was that "he didn't want to be confused as a second gunman."
Think about it.
Of course, this is only the tip of the iceberg where "armed citizens" are concerned--how much more of a problem could they be instead of the boon that the pro-gun side claims.
Unfortunately, this is a subject where the information is horribly biased to present that armed citizens could have stopped these situations. But, do we need to see armed citizens creating more confusion on the scene before this premise is openly questioned?