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Can Mass Shootings Be Prevented?

New research helps identify "red flags" that might help prevent tragedy.

Key points

  • Mass shootings are preventable.
  • Warning signs are often apparent to people who are close to the shooter.
  • Better legal and health care initiatives can yield invaluable dividends in preventing tragedy.

Whenever a mass shooting is reported, whether in the United States or some other country, the inevitable questions arise over what may have motivated the shooter to go on a rampage.

While the term "public mass shooting" typically applies to incidents with four or more victims, the distinction is usually lost on the ones traumatized by witnessing an active shooting, regardless of the actual number of victims involved. Admittedly, there has been a tremendous increase in mass shootings in the past few years. In fact, the five deadliest incidents in U.S. history occurred since 2007 alone, with the average number of victims increasing 47 percent since 2010.

There is also intense speculation over how such tragedies might be prevented, typically by focusing on presumed "causes" such as mental illness, easy availability of guns, or whether they play "shoot-em-up" video games, were bullied, belong to a radical organization, etc. But this fails to explain why the overwhelming majority of people who fall into the same categories do not become mass shooters.

Granted, research has identified a few common characteristics for mass shooters, including:

  • being almost always male (with some prominent exceptions)
  • having a history of mental health problems and social isolation
  • perceiving themselves to be victims
  • having a list of grievances (and often a manifesto released to the press either before or after the incident)
  • having an unhealthy desire for fame or attention (and frequently idolizing previous shooters with whom they identify)
  • having undergone a recent crisis such as job loss, end of a romantic relationship, or legal troubles
  • having easy access to firearms

Another common feature seen in many mass shootings (but far from all of them) is that perpetrators often either kill themselves or set themselves up to be killed by police (.i.e., "suicide by cop".) They also tend to be "lone wolves" acting on their own. Though they may leave behind manifestos expressing support for various extremist movements, their actual participation in the movements may be limited at best since they are rarely "team players" and may be rejected by other movement members for being too "odd."

A new research study published in the Journal of Threat Assessment and Management took a closer look at public mass shooters and what distinguishes them from other homicide offenders. For this research, a team of researchers led by Adam Lankford of the University of Alabama's Department of Criminology and Criminal Justice gathered information from the mass shooter database developed by The Violence Project.

Funded by the National Institute of Justice, the Violence Project database contains records for 171 mass shootings between 1966 to 2019. To be included in the database, mass shooters had to meet the following criteria: "four or more victims are murdered with firearms—not including the offender(s)—within one event, and at least some of the murders occurred in a public location or locations in close geographical proximity (e.g., a workplace, school, restaurant, or other public settings), and the murders are not attributable to any other underlying criminal activity or commonplace circumstance.”

The authors also included additional information from the United States Census Bureau, Centers for Disease Control and Prevention, National Institute of Mental Health, Department of Health and Human Services, Bureau of Labor Statistics, and Pew Research Center allowing them to compare mass shooters with other groups (homicide offenders, suicide victims, and the general population.)

They also drew on existing research examining the prevalence of different mental illness diagnoses in mass shooters versus the general population, as well as demographic comparisons based on age, sex, race/ethnicity, marital status, employment status, military experience, prior felony convictions, and preexisting firearm ownership.

The results showed that although mass shooters were overwhelmingly male (98 percent) and were somewhat younger than the general population, there were no other demographic differences between mass shooters and the general population. This means that there is no way of predicting mass shooters based on demographic "profiles" alone.

Still, while firearm owners in general do not appear to be at risk for becoming mass shooters, the easy accessibility of firearms still appears to be a factor in the prevalence of mass shootings in the United States. This is especially true given that mass shooters are often able to purchase firearms over the counter even after showing multiple warning signs of imminent danger.

How Mass Shooters Differ From the General Population

As expected, there are significant differences between mass shooters and the general population in terms of unemployment (40 percent vs. 4 percent), being unmarried (81 percent vs. 47 percent), having a history of mental health issues (63 percent vs. 19 percent), lifetime thought disorders (26 percent vs. 3 percent), and lifetime suicide ideation (70 percent vs. 16 percent.)

When compared with homicide offenders (committing murder but not meeting the criteria for mass shooters), mass shooters were four times more likely to plan out their attack and eight times more likely to kill strangers than homicide offenders. Mass shooters were also far more likely to commit suicide, whether directly or via "suicide by cop." They were also far more likely than homicide offenders to not be in an active relationship at the time of their attack.

Unfortunately, it likely isn't possible to identify potential perpetrators based on demographic or mental health factors alone. And, as Lankford et al point out, there is no "one size fits all" solution to the problem of mass shootings, either. While mental illness is often blamed for most mass shootings, formally diagnosed mental illness is not a reliable predictor of violence in general. For that matter, mentally ill people are far more likely to be victims of violence than vice versa.

Though research has identified potential warning signs that might indicate that a mass shooting event is imminent, they are often overlooked or ignored until too late. Then again, other factors such as preexisting gun ownership or felony history don't appear to be particularly useful either when it comes to preventing mass shootings.

What Can Be Done?

But Lankford and his co-authors also suggest that many of the strategies already being used to prevent suicides may help prevent mass shootings as well. For example, research has demonstrated that restricting access to firearms is often effective in reducing suicide risk for people displaying signs of suicidal or violent behavior. Such "red flag laws" are becoming increasingly common in many U.S. states, despite Second Amendment court challenges, and may also be passed at the federal level in the foreseeable future.

Another approach may involve adapting mass media suicide prevention campaigns to warn about the dangers of glorifying mass shooters to discourage copycat violence. In the same way that media campaigns describe suicide warning signs, describing mass shooter warning signs may make it easier for vulnerable individuals to be spotted in time.

For now, preventing mass shootings remains a major problem for law enforcement and mental health professionals alike. But nobody contemplating mass violence lives in a vacuum. There will always be teachers, coworkers, friends, and family members who will be the first to recognize that something is wrong and, with the right information, may help prevent yet another senseless tragedy.


Lankford, A., Silver, J., & Cox, J. (2021). An epidemiological analysis of public mass shooters and active shooters: Quantifying key differences between perpetrators and the general population, homicide offenders, and people who die by suicide. Journal of Threat Assessment and Management, 8(4), 125–144.

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