Opinion: The Rise and Decline of Mass Shootings

(March 1) -- When it comes to mass public shootings, the decade doesn't seem to be starting out too well.

Just two months in and already there was a shooting rampage in rural Virginia (which claimed eight lives), one at the University of Alabama (three dead) and other in Denver, near Columbine High School, in which two middle school students were injured.

But the fact is that, while mass public shootings always tend to galvanize massive media coverage, they are becoming increasingly less common, falling sharply in the last decade compared with the previous two. And understanding this decline is important to helping prevent future mass shootings.

The common definition of a mass public shooting is an incident in which four or more victims are killed publicly with guns within 24 hours -- in the workplace, high schools, college campuses, malls, gyms, restaurants and other public places -- excluding shootings in connection with crimes such as robbery, drug trafficking or gang-related activity. By that definition, there have been 140 mass public shootings in the United States during the last 100 years.

Although mass public shootings may seem to be on the rise, newly compiled data show that there were 24 such incidents in the past decade. While that's still significantly higher than the average of the first eight decades of the 20th century, it does mark a significant decline (nearly 50 percent) from the 43 cases in the 1990s (see chart below).

Why have mass public shootings been on the decline?

Highly publicized shootings often renew the call to either loosen or tighten gun laws, but the availability of guns doesn't appear to be much of a factor. Right-to-carry concealed firearms laws do not have a significant impact on mass public shootings, according to a peer-reviewed study I co-authored with Tom Kovandzic and Carl Moody. And rates of gun ownership remained relatively constant in the last several decades of the 20th century, when mass public shootings were on the rise.

More likely, the recent drop is at least in part because of the same complex web of macro-level factors that have been linked to plummeting crime rates since the mid-1990s -- a shift in demographics, increased numbers of police, changing cultural values, etc.

For example, crime rates were relatively low during the 1940s and '50s, and so too were mass murder rates. That was also a time when much of the country saw high rates of marriage, births, jobs, home ownership, church attendance and other pro-social indicators. The generally favorable social conditions over the past 10 to 15 years likewise may have had an impact on crime and, more narrowly, mass public shootings.

In addition, the recent drop in mass public shootings is also likely due to the fact that we are getting better at recognizing, assessing and managing those who pose a legitimate threat of committing this type of violence.

If there's any lesson to be learned from our recent experience with school shootings, it's that promptly notifying authorities in response to violent threats can make a difference. Indeed, it's likely that at least a few of the school shooting plots reported to school and law enforcement officials over the past decade would have resulted in mass shootings had authorities not been alerted.

But the expression of violent threats -- either orally or in writing -- is just one of several common threads that run through mass public shootings. Other telltale markers: The shooters are often white males in their 30s and 40s. They believe they've been mistreated, blaming others for their problems. They feel persecuted, are frequently plagued by mental illness such as depression or schizophrenia, and are, not surprisingly, socially isolated.

Contrary to the popular perception that these offenders "just snap," mass shootings are almost invariably preceded by a great deal of planning and deliberation.

And because they think life is no longer worth living, these shooters are often suicidal. In fact, of the 140 mass public shootings I've examined, a little more than half ended with the shooter committing suicide or forcing the police to kill him. This rate of suicidal behavior is about 10 times that observed among homicides in general.

Given this profile of the mass public shooter, it's critical that we take seriously not only actual violent threats, but also these other warning signs.

It may be difficult to believe that someone we know is capable of committing mass murder. But there have been too many massacres in the past that happened because warning signs were overlooked.

Dr. Grant Duwe, author of "Mass Murder in the United States: A History," is the director of research and evaluation for the Minnesota Department of Corrections. The views expressed here do not necessarily represent those of the Minnesota Department of Corrections.


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