What Exactly Is a Mass Shooting?

Update, December 16, 2012: In the wake of the massacre at Sandy Hook Elementary in Newtown, a story from the Associated Press suggested that mass shootings have not increased in the United States in recent years. But the AP cited research that uses broader criteria than the criteria we used for our investigation, which found an increase. Here is our approach, explained:

What is a mass shooting?
Broadly speaking, the term refers to an incident involving multiple victims of gun violence. But there is no official set of criteria or definition for a mass shooting, according to criminology experts and FBI officials contacted by Mother Jones.

Generally, there are three terms you’ll see to describe a perpetrator of this type of gun violence: mass murderer, spree killer, or serial killer. An FBI crime classification report from 2005 identifies an individual as a mass murderer if he kills four or more people in a single incident (not including himself), typically in a single location. (The baseline of four fatalities is key—more on that just below.)

The primary distinction between a mass murderer and a spree killer, according to the FBI, is that the latter strikes in multiple locations, though still in a relatively short time frame. The third type, a serial killer, is distinguished by striking over a longer time frame, in multiple locations, with opportunity for what the FBI report refers to as “cooling-off periods” in between attacks.

How often do mass shootings occur? 
Beginning in July, after the movie theater slaughter in Aurora, Colorado, we documented and analyzed 62 mass shootings from the last 30 years. As we delved into the research, we realized that robust data on this subject was hard to come by, in part due to the lack of clear criteria. We were focused on the question of how many times Aurora-like events had actually happened. We honed our criteria accordingly:

  • The attack must have occurred essentially in a single incident, in a public place;
  • We excluded crimes of armed robbery, gang violence, or domestic violence in a home, focusing on cases in which the motive appeared to be indiscriminate mass murder;
  • The killer, in accordance with the FBI criterion, had to have taken the lives of at least four people.

The traumatic events included in our guide to mass shootings are the kind that tend to grab national attention—school and workplace shootings, attacks in shopping malls or government buildings—but they represent only a sliver of America’s gun violence, which results in approximately 30,000 deaths annually.

Since the 1980s, the baseline of four fatalities has generally been used for studying mass murder, according to Professor James Alan Fox of Northeastern University, who has written multiple books on the subject. But as Fox agreed when we spoke, that baseline ultimately is arbitrary. Was it not a “mass shooting” in 2008, for example, when a man walked into a church in Tennessee and opened fire with a shotgun, killing two and injuring seven? Dropping the number of fatalities by just one, or including motives of armed robbery, gang violence, or domestic violence, would add many, many more cases to the list.

According to a recent report in Time magazine (available only to subscribers, and whose criteria is unclear), there’ve been “nearly 20 mass shootings” every year on average during the last three and a half decades.

Why didn’t you include the infamous DC Beltway sniper attacks on your mass shootings map?
We’ve been asked this question numerous times. The man who killed 10 and wounded 3 others a decade ago (along with a young accomplice) was a serial killer: He committed multiple attacks over several weeks, in different locations. It was a particularly tense time for people living in the DC metro area—the shooter “terrorized our neighborhood,” as one person wrote to me in an email—but the case did not fit the criteria described above.

Is Mother Jones focusing on this stuff as part of a conspiracy to take away Americans’ gun rights?
No. One of our lead reporters on this beat, Adam Weinstein, who covered the Trayvon Martin killing and investigated how the National Rifle Association helped spread “Stand Your Ground” laws nationwide, is a Navy veteran and third-generation gun owner. Multiple other Mother Jones staffers are experienced with guns.

The debate over guns in the United States is extremely contentious and polarizing, and we think that the more reporting and clear data available about guns, the better. That mass shootings keep happening is an undeniable fact. Why they do, and how to stop them, is a matter for further investigation.

Update, January 8, 2013: Where can I learn more about MoJo’s investigation?
See our recently published America Under the Gun: a Special Report on gun laws and the rise of mass shootings, which contains interactive maps, charts, and dozens of stories from over the last year.

 

AN IMPORTANT UPDATE

We’re falling behind our online fundraising goals and we can’t sustain coming up short on donations month after month. Perhaps you’ve heard? It is impossibly hard in the news business right now, with layoffs intensifying and fancy new startups and funding going kaput.

The crisis facing journalism and democracy isn’t going away anytime soon. And neither is Mother Jones, our readers, or our unique way of doing in-depth reporting that exists to bring about change.

Which is exactly why, despite the challenges we face, we just took a big gulp and joined forces with the Center for Investigative Reporting, a team of ace journalists who create the amazing podcast and public radio show Reveal.

If you can part with even just a few bucks, please help us pick up the pace of donations. We simply can’t afford to keep falling behind on our fundraising targets month after month.

Editor-in-Chief Clara Jeffery said it well to our team recently, and that team 100 percent includes readers like you who make it all possible: “This is a year to prove that we can pull off this merger, grow our audiences and impact, attract more funding and keep growing. More broadly, it’s a year when the very future of both journalism and democracy is on the line. We have to go for every important story, every reader/listener/viewer, and leave it all on the field. I’m very proud of all the hard work that’s gotten us to this moment, and confident that we can meet it.”

Let’s do this. If you can right now, please support Mother Jones and investigative journalism with an urgently needed donation today.

payment methods

AN IMPORTANT UPDATE

We’re falling behind our online fundraising goals and we can’t sustain coming up short on donations month after month. Perhaps you’ve heard? It is impossibly hard in the news business right now, with layoffs intensifying and fancy new startups and funding going kaput.

The crisis facing journalism and democracy isn’t going away anytime soon. And neither is Mother Jones, our readers, or our unique way of doing in-depth reporting that exists to bring about change.

Which is exactly why, despite the challenges we face, we just took a big gulp and joined forces with the Center for Investigative Reporting, a team of ace journalists who create the amazing podcast and public radio show Reveal.

If you can part with even just a few bucks, please help us pick up the pace of donations. We simply can’t afford to keep falling behind on our fundraising targets month after month.

Editor-in-Chief Clara Jeffery said it well to our team recently, and that team 100 percent includes readers like you who make it all possible: “This is a year to prove that we can pull off this merger, grow our audiences and impact, attract more funding and keep growing. More broadly, it’s a year when the very future of both journalism and democracy is on the line. We have to go for every important story, every reader/listener/viewer, and leave it all on the field. I’m very proud of all the hard work that’s gotten us to this moment, and confident that we can meet it.”

Let’s do this. If you can right now, please support Mother Jones and investigative journalism with an urgently needed donation today.

payment methods

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate