News Gun Violence Initiative Behavioral/ Mental Health Violence & Abuse

Gun violence expert speaks on prevention, shooter characteristics and mental health implications

Written by Kim Furlow, communications manager for the Institute for Public Health


The Department of Psychiatry at Washington University School of Medicine along with the Institute for Public Health recently welcomed renowned gun violence expert and Forensic Psychologist, Jillian Peterson, PhD, for a special presentation, “Mental illness and gun violence: Solutions for St. Louis”. Peterson is professor of criminology at Hamline University and author of the highly acclaimed book, The Violence Project: How to Stop a Mass Shooting Epidemic.

Moderated by the head of WashU’s Department of Psychiatry, Eric Lenze, MD, and William G. Powderly, MD, the Larry J. Shapiro Director of the Institute for Public Health, the event was attended by more than 350 staff, students and community members. Peterson discussed her landmark study on mass shooters; the common characteristics of people who commit violence using firearms; and she suggested solutions to gun violence as a critical public health issue. The majority of the information presented can be located on Peterson’s webpage,

Facts about gun violence

Peterson outlined forms of gun violence that have caused it to become one of the most concerning crises affecting St. Louis and the U.S. today.  “Gun violence” is a catchall term which includes many tragedies: suicide (approximately 24,000 deaths/year in the U.S.), community gun homicide mostly related to personal conflicts and criminal activity (18,000 deaths/year), domestic violence (2,000 deaths/year), unintentional shootings (500 deaths/year), and police-involved shootings (1,000 deaths/year).

Mass shootings are a separate category from all of the above. They cause approximately 100 deaths each year, a far smaller number than the above, but have outsized influence given their adverse psychological consequences not just for survivors but also for the community and nation at large. Peterson noted that there is now a significant mass shooting-related industry in the U.S. that, for example, sells bulletproof children’s backpacks to worried parents.

She defined “mass shootings” as more than four people killed in a public place, reminding the audience that they need to only look at the latest news to learn that, over the last decade, mass public shootings and their number of victims have increased in frequency. More specifically, during 2020-21, suicides and gun homicides in our nation marked their greatest increase in history. Peterson also noted that during the pandemic, there was a huge rise in gun sales, particularly among first time buyers. In the U.S. today, there are now 1.25 guns owned per person.

As part of her groundbreaking Violence Project, Peterson’s team built a comprehensive database of mass shooters and guns used in mass shootings. Found on her website,, the database “contains lots of data for non-partisan discussion about violence”.

Peterson described common denominators among perpetrators of gun violence:  

  • In the past five years, the largest increase in mass shootings has occurred at retail locations
  • Common characteristics of mass shooters include:
    • 98% male
    • 80% white, and on average, between 18-22 years old
    • Mass shooters are “insiders” associated with the location at which the shooting takes place; may be someone who worked there or may be closely associated with someone who works there
    • Perpetrators are in crisis and have probably recently exhibited noticeable changes in behavior (versus how they normally act)
    • Shooters are suicidal; they go in knowing how they will end up
    • Their goal is to make history. They know they will not get away with the act.
Does mental illness cause mass shootings?

Peterson believes that there are variables as to why mass shootings occur. Mental illness is typically not the sole cause however, approximately 70% of mass shooters have some mental health history, and approximately one-quarter have evidence of a serious mental illness (e.g., thought disorder).

Additional shooter and mass shooting characteristics found in Peterson’s study include:

Shooters plan violence and often leak their plans to others. Ninety percent of mass shooters at K-12 educational facilities told their peers. “Leakage”, as Peterson calls it, is key to prevention. “If we can reach the person at the point of them leaking plans, we might be able to prevent the crime,” she said.

According to Peterson’s study, the most common gun used to commit violence is a handgun (47%), usually taken from home. In the last seven years however, assault rifle usage has risen as well as the wearing of tactical vests. Shooters identify with previous mass shooters and mimic them. Peterson added that two weeks after one shooting is a primary time in which another will occur. There is a typical historical profile of mass shooters. Peterson suggested that we could think of prevention during any points of this spectrum:

According to her study, perpetrators of violence are usually “insiders” at the place where shootings occur, so prevention efforts such as safety pre-drills often don’t work. Shooters could be aware of safety protocols, or already “know the drill”.

So, what can we do?

Peterson’s study suggests the need for holistic safety, which addresses the complete systems of pathways and precursors to violence. This holistic violence prevention needs to respond to the root causes of violence at the individual, institutional and societal levels.

Similar to CPR training to save someone’s life, Peterson recommends crisis intervention training to help prevent future gun violence:

  • Promote a safe school climate
  • Establish team w/variety of personnel (security personnel, mental health professional, peer/parent)
  • Identify resources (communications, substance abuse experts, housing or other family resources for those in need)
  • Define what behavior should be reported
  • Create centralized reporting system (safe feeling increases reporting)
  • Responding to the crisis (make a plan)

Peterson mentioned the “Sandy Hook Promise” as a good example of an effective reporting system. “Say Something” is the group’s anonymous reporting system. She also pointed out that when we have strong social connections in our schools and work communities, we have better personal health. This philosophy, though, is diametrically opposed to how a person with mental illness is often treated by peers or colleagues.

A lot of the time, the dangerous person is expelled, shut out, which exacerbates rage and propensity for violence.

Jillian Peterson, gun violence expert, author

Other ways to help stop violence before it happens include:

  • Peterson recommends that instead of being inclusive, find ways to support the person, rather than excluding them (i.e., shutting them out of society).
  • Safe gun storage is one response that cannot be stressed enough, Peterson added. How to safely store firearms can (and should be) best shared through public communication campaigns.
  • Mass shootings are MEANT to go viral, Peterson said. We can help prevent future incidences by NOT publishing manifestos.

Following Peterson’s presentation, she sat on a panel alongside Cynthia Rogers, MD, the Blanche F. Ittleson Professor of Psychiatry and director of the Division of Child & Adolescent Psychiatry at the Washington University School of Medicine in St. Louis. Also on the panel was Associate Professor of Emergency Medicine, Kristen Mueller, MD, a faculty lead for the Life Outside of Violence Program at WashU’s Institute for Public Health.

“What are Washington University and BJC Healthcare doing about gun violence prevention?”

Rogers: Both entities arehelping caregivers by addressing their health through training and support services. There is also a focus on caregivers of children under age seven, a point of highest risk for accessing guns at home. There are parent training services and behavioral assistance programs available for parents whose children are exhibiting behavioral issues at a young age. Rogers also discussed using programming in schools to help those who have experienced childhood trauma.

Mueller: WashU’s Life Outside of Violence program uses a regional approach to help those harmed by violence to receive the treatment, support and resources they need to find alternatives to end the cycle of violence. LOV case managers help individuals age 8-30 manage medical care first, then provide wrap-around care via housing and utilities assistance as needed and help individuals and their families set goals in their community. There is a significant decrease in re-injury, retaliation, and violent injury among individuals treated at LOV partner hospitals. Mueller added, “Kids know where guns are in house. Safe storage conversations MUST happen.”  

“Do violent video games cause violence acts?”

Peterson: Violent video game use among K-12 shooters is prominent; however, evidence shows that even though these games might be an accelerant, there is no solid evidence that they directly cause violence. Regarding violence in houses of worship: Incidences are generally hate driven or, there is a domestic relation inside who is unguarded. Greeters & sharing de-escalation strategies with staff is suggested.

In all, many event attendees felt that the information provided was useful and cathartic. Drs. Lenze and Powderly concurred that more action to prevent gun violence is necessary.

There are real solutions to some of the most tragic gun violence problems. Suicide prevention and crisis management strategies can help people in distress, and thereby reduce the risk of mass shootings and other types of gun violence. I hope that St Louis can come together to make these solutions a reality.

Eric Lenze, head of the Department of Psychiatry at Washington University School of Medicine in St. Louis