Sadly, many of these incidents were not completely thwarted. Several innocents were harmed and killed before the attackers being stopped. Many studies discount these incidents because they weren’t actual mass shootings, because not enough people died before they were stopped.
It’s difficult to tally mass shooting or killing incidents simply based on the number of victims. In many cases when the incidents are thwarted – by police, armed citizens, or anyone – the number of victims is below any arbitrary threshold and does not reflect the number of lives saved by the intervention.
These stories were chosen because the attacker was threatening 4 or more people and, had the attacker not been stopped, would have killed or seriously injured more innocents (as best can be reasonably assumed without a crystal ball).
Father stops potential mass shooter at McDonald’s. AL.com (archive), WBRC, 2, 3 (archive, 2, 3), Fox News (archive), MSN (archive), WVTM13 (archive)
Man enters crowded auto center in Rockledge, Florida, kills 1, paralyzes another, stopped by two employees with guns of their own. Florida Today, WFTV video
Gunman opened fire at Burnette Chapel Church of Christ in Antioch, Tennessee, killing one, wounding seven others. Gunman held for police by usher. WKRN, Fox News, Wikipedia
“Hero” stopped mass murder by crazed bar patron who was armed to the teeth, police say. Dallas News
Man opens fire in Playoffz nightclub in South Carolina, hitting three. Patron returns fire. Fox 5 Atlanta
Uber driver with carry permit shoots gunman in Chicago’s Logan Square. Chicago Tribune, Sun-Times
Firefighters with concealed carry permits may have prevented massacre of children and other firefighters by crazed gunman. Fox Carolina
Passerby with concealed handgun hears gunshots in barbershop and kills attacker. NBC Philadelphia
Ex-employee attacks former co-workers with knife, beheads one, shot and stopped by COO. KFOR, Wikipedia
Mercy-Fitzgerald Hospital psychiatric patient kills caseworker, shoots doctor. Stopped from killing more by doctor with a gun. NBC Philadelphia
Group leaving party comes under fire from multiple attackers. Concealed carrier returns fire, hits one, as group flees. Chicago Tribune
Ex-construction worker opens fire on former co-workers, shot by foreman with carry permit. KXAN
Man refused entry to strip club after racist remarks in line, returns in mask to shoot at occupants, shot by a bouncer. KATU, Oregon Live (1), Oregon Live (2)
Gunman shoots patrons at Bonnie’s Bar in Plymouth, PA, stopped by concealed carrier who shot him. WNEP
Church shooting in Aurora, Colorado, just months before the infamous theater shooting. Unlike the theater shooting, this was not a gun-free zone. The shooter killed the pastor’s mother and was then immediately stopped by an armed parishioner before he could shoot anyone else. KDVR, Freedom Outpost
Potential mass shooting at Freewill Baptist Church in South Carolina averted as concealed carrier holds gunman at bay. GoUpstate
Gunman at New Life Church in Colorado Springs stopped by volunteer security guard with a gun. 5280 archived story, Wikipedia
14-year-old enters Parker Middle School dance with .25 caliber pistol, kills one, wounds 3 others. Venue owner confronts him with a shotgun and holds him until police arrive. CNN, Wikipedia
Assistant principal stops school shooting at Perl High School, Mississippi with handgun retrieved from car. Lubbock Avalanche-Journal archived story, Wikipedia
Parishioner Charl van Wyk fights 4 attackers armed with machineguns, hand-grenades, and molotov cocktails. Wikipedia, American Warrior Show Interview