Do citizens (not police officers) with guns ever stop mass shootings?

Backers of laws that let pretty much all law-abiding people carry concealed guns in public places often argue that these laws will sometimes enable people to stop mass shootings. Opponents occasionally ask: If that's so, what examples can one give of civilians armed with guns stopping such shootings? Sometimes, I hear people asking if even one such example can be found, or saying that they haven't heard of even one such example.

A while back I posted about a few examples, but since then there have been some more, so I thought I'd note them. Naturally, such examples will be rare. Even in states which allow concealed carry, there often aren't people near a shooting who have a gun on them at the time. Many mass shootings happen in supposedly "gun-free" zones (such as schools, universities, bars, or private property posted with a no-guns sign), in which gun carrying isn't allowed in many states. And there is no central database of such examples, many of which don't hit the national media, especially if a gunman is stopped before he shoots many victims. Moreover, at least some examples are ambiguous, because it might be unclear - as you'll see below - whether the shooter had been planning to kill more people when he was stopped.

Still, for whatever they are worth, here is a list of some such incidents (which deliberately excludes killings stopped by people who were off-duty police officers, or police officers from other jurisdictions, at the time of a shooting, as well as some other cases which struck me as borderline):

1. In Chicago earlier this year, an Uber driver with a concealed-carry permit "shot and wounded a gunman [Everardo Custodio] who opened fire on a crowd of people."

2. In a Philadelphia barber shop earlier this year, Warren Edwards "opened fire on customers and barbers" after an argument. Another man with a concealed-carry permit then shot the shooter; of course it's impossible to tell whether the shooter would have kept killing if he hadn't been stopped, but a police captain was quoted as saying that, "I guess he [the man who shot the shooter] saved a lot of people in there."

3. In a hospital near Philadelphia, in 2014, Richard Plotts shot and killed the psychiatric caseworker with whom he was meeting, and shot and wounded his psychiatrist, Lee Silverman. Silverman shot back, and took down Plotts. While again it's not certain whether Plotts would have killed other people, Delaware County D.A. Jack Whelan stated that, "If the doctor did not have a firearm, (and) the doctor did not utilize the firearm, he'd be dead today, and I believe that other people in that facility would also be dead"; Yeadon Police Chief Donald Molineux similar said that he "believe[d] the doctor saved lives." Plotts was still carrying 39 unspent rounds when he was arrested. [UPDATE: I added this item since the original post.]

4. In Plymouth, Pa., in 2012, William Allabaugh killed one man and wounded another following an argument over Allabaugh being ejected from a bar. Allabaugh then approached a bar manager and Mark Ktytor and reportedly pointed his gun at them; Ktytor, who had a concealed-carry license, then shot Allabaugh. "The video footage and the evidence reveals that Mr. Allabaugh had turned around and was reapproaching the bar. Mr. [Ktytor] then acted, taking him down. We believe that it could have been much worse that night," Luzerne County A.D.A. Jarrett Ferentino said.

5. Near Spartanburg, S.C., in 2012, Jesse Gates went to his church armed with a shotgun and kicked in a door. But Aaron Guyton, who had a concealed-carry license, drew his gun and pointed it at Gates, and other parishioners then disarmed Gates. Note that in this instance, unlike the others, it's possible that the criminal wasn't planning on killing anyone, but just brought the shotgun to church and kicked in the door to draw attention to himself or vent his frustration.

6. In Atlanta in 2009, Calvin Lavant and Jamal Hill broke into an apartment during a party and forced everyone to the floor. After they gathered various valuables, and separated the men and the women, and Lavant said to Hill, "we are about to have sex with these girls, then we are going to kill them all," and began "discussing condoms and the number of bullets in their guns." At that point, Sean Barner, a Marine who was attending Georgia State as part of the Marine Enlisted Commissioning Education Program, managed to get to the book bag he brought to the party; took out his gun; shot and scared away Hill; went into the neighboring room, where Lavant was about to rape one of the women; was shot at by Lavant, and shot back and hit Lavant, who then ran off and later died of his injuries. One of the women was shot and wounded in the shootout, but given the circumstances described in the sources I linked to, it seemed very likely that Lavant and Hill would have killed (as well as raped) some or all of the partygoers had they not been stopped. This incident of course involves a member of the military, not a civilian, so some may discount it on those grounds. But Barner was acting as a civilian, and carrying a gun as a civilian (he had a concealed carry license); indeed, if he had been on a military base, he would generally not have been allowed to carry a gun except when on security duty. [UPDATE: I added this item since the original post.]

7. In Winnemucca, Nev., in 2008, Ernesto Villagomez killed two people and wounded two others in a bar filled with 300 people. He was then shot and killed by a patron who was carrying a gun (and had a concealed-carry license). It's not clear whether Villagomez would have killed more people; the killings were apparently the result of a family feud, and I could see no information on whether Villagomez had more names on his list, nor could one tell whether he would have killed more people in trying to evade capture.

8. In Colorado Springs, Colo., in 2007, Matthew Murray killed four people at a church. He was then shot several times by Jeanne Assam, a church member, volunteer security guard and former police officer (she had been dismissed by a police department 10 years before, and to my knowledge hadn't worked as a police officer since). Murray, knocked down and badly wounded, killed himself; it is again not clear whether he would have killed more people had he not been wounded, but my guess is that he would have (UPDATE: he apparently went to the church with more than 1,000 rounds of ammunition).

9. In Edinboro, Pa., in 1998, 14-year-old Andrew Wurst shot and killed a teacher at a school dance, and shot and injured several other students. He had just left the dance hall, carrying his gun - possibly to attack more people, though the stories that I've seen are unclear - when he was confronted by the dance hall owner James Strand, who lived next door and kept a shotgun at home. It's not clear whether Wurst was planning to kill others, would have gotten into a gun battle with the police, or would have otherwise killed more people had Strand not stopped him.

10. In Pearl, Miss., in 1997, 16-year-old Luke Woodham stabbed and bludgeoned to death his mother at home, then killed two students and injured seven at his high school. As he was leaving the school, he was stopped by Assistant Principal Joel Myrick, who had gone out to get a handgun from his car. I have seen sources that state that Woodham was on the way to Pearl Junior High School to continue shooting, though I couldn't find any contemporaneous news articles that so state. [UPDATE: For whatever it's worth, Heidi Kinchen of The Advocate (Baton Rouge) notes that Myrick was in the Army reserves and in the National Guard, though he was obviously not on duty at the time of the shooting.]

Of course there's much we don't know about civilians and mass shootings: In what fraction of mass shootings would such interventions happen, if gun possession were allowed in the places where the shootings happen? In what fraction would interventions prevent more killings and injuries, as opposed to capturing or killing the murderer after he's already done? In what fraction would interventions lead to more injuries to bystanders?

Finally, always keep in mind that mass shootings in public places should not be the main focus in the gun debate, whether for gun control or gun decontrol: They on average account for much less than 1 percent of the U.S. homicide rate and are unusually hard to stop through gun control laws (since the killer is bent on committing a publicly visible murder and is thus unlikely to be much deterred by gun control law, or by the prospect of encountering an armed bystander). Still, people had asked for examples of some shootings in which a civilian armed with a gun intervened and brought down the shooter, so here is what I found.

For an explanation of why I didn't include the December 2012 Clackamas Mall shooting, see here. Some of these incidents are drawn from a list on the Crime Prevention Research Center site, though I have independently read the media reports to which I linked (as well as some other media reports on the incidents, for background).

UPDATE: I originally called this post, "Do civilians with guns ever stop mass shootings?," using "civilians" to set aside mass shootings stopped by on- or off-duty police officers. But after learning that Myrick (#10) was a National Guard member, and that Barner (#6) was a Marine, I changed that to "citizens (not police officers)." I think including the military members is still helpful, because they were acting as civilians, and were not on duty, on base, or otherwise different from other citizens (though of course they had weapons training and the experience of military discipline, something that many millions of former military members also have). But I note their military membership above, so people who want to set them aside and focus on the other eight examples can do so.