Mass killings since 2015: Could proposed laws have made a difference?

People mourn during a vigil for 23 people that were killed at a Walmart in El Paso, Texas, on Aug. 5, 2019. (Michael Robinson Chavez/The Washington Post)
People mourn during a vigil for 23 people that were killed at a Walmart in El Paso, Texas, on Aug. 5, 2019. (Michael Robinson Chavez/The Washington Post)

With numbing frequency — an average of six times a year since 2015 — a person with a firearm has committed mass murder in a public place in the United States.

And after each tragedy, a familiar question arises: Could it have been prevented? This question has become acute once again in the aftermath of the deaths of 19 children and two teachers in Uvalde, Tex., and 10 others days earlier at a supermarket in a predominantly Black community of Buffalo.

President Biden has called on lawmakers to adopt proposals he has previously supported, and a bipartisan group of 20 senators agreed over the weekend to a tentative framework of modest gun-safety reforms coupled with spending on school security and mental health programs. The accord on Tuesday won the endorsement of Republican Leader Mitch McConnell of Kentucky, a longtime defender of gun rights.

To assess whether new gun restrictions being discussed today could have prevented incidents such as the ones in Uvalde and Buffalo, we analyzed 41 gun-related mass killings since 2015 alongside the litany of proposed restrictions that are backed by major gun-control groups and prominent in today’s national debate.

The takeaway is nuanced: Only about one-third of these mass killings might have been prevented by any major proposals. But some ideas — such as not allowing people under age 21 to buy assault rifles and banning ammunition storage and feeding devices known as magazines that hold more than 10 rounds — might have minimized the bloodshed. Improvements to the country’s background check system could make a difference as well, though it’s not clear how many lives would have been saved by the relatively modest changes that are part of the tentative Senate agreement, which would require a mandatory search of juvenile justice and mental health records of buyers younger than 21 and seek to clarify who needs to obtain a federal firearm license.

The incidents analyzed here represent cases in which four or more individuals, not including the assailant(s), were killed by gunfire in a public setting within a 24-hour period. This report does not take into account the vast majority of incidents of gun violence in the United States, including those that disproportionately affect communities of color. And it’s important to note that gun restrictions could help reduce overall gun violence even if mass shootings are not eliminated.

This report is an update of a 2015 fact check of a statement by Sen. Marco Rubio (R-Fla.) that none of the mass shootings that had taken place in the previous three years would have been prevented by proposed gun laws pending in Congress. At the time, we examined 12 mass shootings over three years and determined that Rubio was right. The 41 incidents analyzed in this report represent mass killings involving guns that have taken place since then.

Why is it so difficult to stop these mass killings?

For starters, restricting the flow of guns in the United States is a difficult task.

Unlike people in many other countries, Americans have tremendous freedom to acquire and possess firearms. In most states, a license or firearms training is not required. Under federal law, Americans buying handguns from licensed dealers must be at least 21 but in most states rifles can be purchased at age 18. There is no federal minimum age for possession of a rifle or shotgun. Firearms are prohibited to a narrow group of people — such as those convicted of a felony — but can often be obtained illegally or even built.

Some of the highest profile shootings involved semiautomatic rifles — i.e., AR-15 variants often called “assault weapons.” But a much greater number took place with only handguns or the assailants included handguns as part of their arsenal. A limited assault-weapons ban (which was riddled with loopholes) was in place from 1994 to 2004 before Congress let it lapse. The National Shooting Sports Foundation says nearly 20 million such weapons are now in circulation in the United States. Prospects for reviving the ban are practically nil and, if such a ban were ever imposed again, presumably the ownership of such weapons would be grandfathered, as they were in the previous ban.

The analysis also shows how laws already implemented sometimes fail to work. Existing state laws banning assault weapons or large-capacity magazines did not stop some shooters from obtaining these items. Other times, federal laws failed to prevent the transfer of a weapon to a person with mental health issues, a felon or even a former soldier who had been discharged who then became a mass shooter.

To be sure, the occasional failure of existing laws does not mean those laws did not effectively thwart other dangerous people from obtaining firearms. A University of California-Davis study released June 7, for instance, found that as many as 58 mass shootings might have been prevented in California after the state in 2016 implemented the first red-flag law, allowing a person’s firearms to be seized when the imminent risk of violence appears high. Six of the cases involved minors, all of whom targeted schools, the study said, while almost 30 percent had an assault-type rifle that was temporarily removed with a restraining order.

In two cases since 2015, federal laws or regulations were changed as a result of a mass killing, indicating that the event was horrific enough that it spurned some action. In three cases, state laws were changed to raise the minimum age to purchase a rifle from 18 to 21.

For this analysis, in each case, we examined whether certain gun-control proposals might have made a difference in how the guns were obtained and whether existing laws worked as intended. We did not consider proposals that have been enacted in other countries but have little if any hope of passage even on the state level, such as mass confiscation of guns. We also did not consider some elements of the tentative Senate agreement, either because the proposals are still too vague without legislative language or generally would not apply to mass killings.

Instead, we focused on proposals that have been repeatedly proposed by Biden and gun-safety organizations. The tentative Senate agreement would touch on a couple of these proposals, as noted below.

Our analysis shows that a combination of new rules could have an impact in the effort to thwart potential mass killers. This package would include requiring secure gun storage, permits to buy a firearm, an increase in the legal age to buy a semiautomatic rifle and more robust red-flag laws.

Expand any of the categories below to see which proposed laws, if any, would have prevented each mass shooting we looked at.
14 incidents
2 incidents
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We developed a list of 41 mass killings since 2015, using a database created for an upcoming paper for the Justice Department, written by a team led by James Alan Fox of Northeastern University, Grant Duwe of the Minnesota Department of Corrections and Michael Rocque of Bates College. They define a “mass public shooting” is any event in which four or more individuals, not including the assailant(s), were killed by gunfire in a public setting within a 24-hour period. That database goes through 2020, so we supplemented it with shootings in 2021 and 2022 that meet their criteria from the Mother Jones database of U.S. mass shootings.

Mass shootings associated with profit-motivated criminal activity (such as gang activity, robbery, drug trade and elimination of witnesses) and domestic violence (such as a parent killing the rest of the family) generally are excluded from the database. This allows researchers to focus on the mass shootings that “closely align with the fears that many Americans have concerning seemingly senseless and sometimes indiscriminate shootings with large numbers of fatalities that occur in a public place,” the paper says.

That definition, however, may leave out many mass-shooting events that especially affect communities of color. Nearly 50 percent of shootings with four or more fatalities involved a gunman who kills his family members (followed by suicide) and nearly 20 percent are profit-motivated, the paper says. How the killer obtained the firearm for these murders is always not clear from the public record.

To distinguish from shooting events in which at least four people are killed or injured, for this report we have chosen to label these events as “mass killings.”

Details about the 41 mass killings were obtained by the Fact Checker from media reports and official documents. In four mass killings in this period not enough information could be obtained from the public record about the source of the firearms to make an evaluation, so they are not included in the above summary.


Story editing by Peter Wallsten. Copy editing by Brandon Standley. Visual editing by Kainaz Amaria. Video editing by Adriana Usero. Photo editing by Karly Domb Sadof. Design editing by Madison Walls. Design and development by Tyler Remmel. Additional support from Jake Crump.