Mass killings and civilians shooting back
A few days ago I linked to a study of mass killings stopped by police vs. stopped by civilians, finding that the average death rate of those stopped by police was 14.3, and the average death rate of those stopped by civilians was 2.33. Not surprising, since the armed civilians are usually on the scene, while police necessarily respond many minutes later. The killers are not stupid: they don't attack if a uniformed LEO is within sight. The result suggest what Joe Olson said years ago: in a situation with an "active shooter" who is willing to die, the only thing that stops him is quick and accurate return fire from someone not in a police uniform. Whether that person is an off-duty officer or an armed civilian doesn't matter.
I posted below to a story indicating that the Clackamas Town Center shooter may have stopped and committed suicide because he saw a CCW holder who drew and had him in his sights. Here's more on the story.
Now comes a story of an apparent attempt at a mass slaying in Texas, which was halted when an off-duty officer shot the attacker. Total casualties, apart from the perp, were one man wounded.
I'd say we're seeing a pattern here.