Federal Assault Weapons Ban could have prevented 38 mass shootings since 2005

• Link to: Northwestern Now Story

• Ban prevented up to five public mass shootings when it was active (1994-2004)
• First study to consider how many mass shootings would have been prevented had the ban remained in place
• ‘Most Americans, despite political affiliation, believe in responsible gun ownership’

CHICAGO --- The Federal Assault Weapons Ban (FAWB) prevented up to five public mass shootings when it was active between 1994 and 2004, according to previous research. Had the ban stayed in place, it would have prevented up to 38 more mass shootings between 2005 and 2022, a new Northwestern Medicine study has found.

Enacted by Congress in 1994, the ban prohibited the sale and manufacture of certain military-style semiautomatic weapons and high-capacity magazines in the U.S. There have been multiple attempts to renew the ban, but none have succeeded.

Most research has focused on whether the number of mass-shooting deaths declined during the FAWB. This is the first study to consider how many mass shootings would have been prevented had the ban remained in place. 

“It is intuitive that shooters with rapid-firing, machine-gun-like military weapons with large-capacity magazines can quickly fire and kill or injure dozens of people in just seconds compared to shooters with pistols, revolvers, rifles or shotguns,” said senior author Lori Post, professor of emergency medicine and medical social sciences at Northwestern University Feinberg School of Medicine. “However, there are only two investigations into whether a prohibition of assault weapons prevents mass shootings from even occurring. It certainly does.”

The findings were published Sept. 20 in the journal JMIR Public Health and Surveillance.

“Nobody wants to be a victim of these seemingly random events, and nobody wants to worry that their children are going to die at school,” Post said. “Most Americans, despite political affiliation, believe in responsible gun ownership. We need to prevent mass shooter wannabees from obtaining assault rifles — because many need an assault rifle to carry out the mass shooting.”

The study found the FAWB was successful at stopping potential mass shooters from committing a mass shooting. It also demonstrates that would-be mass shooters did not substitute other weapons for assault weapons and large-capacity magazines, as those types of mass shootings did not change during the assault weapons ban.

“One of the more interesting parts of this work is the separation of results into mass shootings where the shooter did or did not bring an assault weapon to the event,” said first author Alexander Lundberg, assistant professor of emergency medicine at Feinberg. “During the FAWB, we found a downward trend in mass shootings where a perpetrator did bring an assault weapon. However, we found no difference in trends for mass shootings where the perpetrator did not bring an assault weapon. These results suggest that the FAWB discouraged potential perpetrators from committing a mass shooting with an assault weapon, and, furthermore, that these potential perpetrators did not simply carry out attacks with other types of weapons.”

How the scientists estimated 38 thwarted mass shootings

The scientists define a public mass shooting as an event in a public place where there are at least four people killed by a firearm, not including the perpetrator, within a 24-hour time period. Using that definition, the study included all public mass shootings (a total of 184) that occurred between 1966 (when the FBI began tracking them) and 2022. The scientists used linear regression on a simple moving average of mass shootings per year. They looked at the trends before, during and after the ban was put in place and controlled for the national homicide rate. After estimation, the model provided counterfactual estimates of public mass shootings in two hypothetical scenarios; if the FAWB were never imposed and if the FAWB remained in place.

Could a ban like this ever be reinstated?

Given the large amount of people who have purchased assault weapons over the past two decades since the FAWB expired, Post said a future ban would need to include a buyback program or exclude a “grandfather” clause, unlike the last one.

“We won’t be able to stop all mass shootings — especially those committed by a jilted husband or a fired employee who reacts and kills people they know with whatever gun they have,” Post said. “However, a ban on assault weapons and large-capacity magazines would surely thwart mass shootings committed by those mass killers who spend weeks to months planning a mass shooting or those who want to be famous and have fantasies, such as dressing up in a pseudo-commando costume, which includes an assault rifle.

Other study authors from Northwestern include Maryann Mason and David Victorson.

Funding for the study, “Public Mass Shootings: Counterfactual Trend Analysis of the Federal Assault Weapons Ban,” was provided by an anonymous foundation donor.