The FBI examined 160 shootings between 2000 and 2013 and found that most of the violence ended when the assailant stopped shooting, committed suicide, or fled. Unarmed citizens successfully restrained shooters in 21 of those incidents, according to the FBI. Two attacks stopped when off-duty officers shot and killed the attackers. Five ended in much the way the attack at Louie’s did — when armed civilians, mostly security guards, exchanged fire with the shooters.

In November, Stephen Willeford, a former NRA instructor, shot a gunman who killed more than two dozen people inside a church in Sutherland Springs, Texas, hitting the attacker twice. The shooter fled and later shot himself in the head while under chase. And in June, a pastor and volunteer firefighter who had been through active-shooter training killed a carjacker who opened fire inside a Walmart store in Tumwater, Washington.

But interventions by “Good Samaritans” also have ended in tragedy.