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Understanding the Mind of Mass Shooters: Psychological Autopsy

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By Leischen Stelter, editor of In Public Safety

Orlando, San Bernardino, Sandy Hook, Aurora, Isla Vista: The list of places where unstable individuals have conducted violent attacks goes on and on. What causes these individuals to resort to violence? What are the behavioral characteristics that police, intelligence analysts, family members and even strangers can look for to identify the next mass shooters?

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On June 21, during the 6th annual Mid-Atlantic INLETS: Violent Crimes & Terrorism Trends seminar in Annapolis, Maryland, Supervisory Special Agent Robert Gaskamp, a profiler with the FBI’s Behavioral Analysis Unit (BAU), and Jennifer Tillman, a crime analyst with BAU, presented a case study on the ambush and murder of two Las Vegas Metropolitan Police officers and one bystander.

Two officers, Alyn Beck and Igor Soldo, were ambushed while eating lunch at a Cici’s Pizza restaurant on June 8, 2014. The officers were killed by husband and wife Jerad and Amanda Miller. After killing the officers, the Millers went across the street and barricaded themselves inside a Walmart, killing one shopper, before they were shot and killed by police.

Gaskamp started by describing and showing videos of the attacks and the police response. The analysts then provided a psychological autopsy of the mass shooters to help law enforcement identify behavioral warning signs of violent attackers.

Psychological Autopsy of Mass Shooters

While every case is different, there are often warning signs that police, family members, peers and even strangers can use to identify potential mass shooters. In addition, there are often similarities in personality traits of attackers that may indicate instability and violent tendencies.

Personality Characteristics

Jerad was a 31-year-old white male who came from a controlling religious background. He had been convicted of animal cruelty as a teenager, was a high school dropout and held only sporadic employment throughout his life. He was financially irresponsible, a consistent substance abuser and had a deviant pornography obsession involving violence and pain. Psychologists noted that he displayed characteristics of a person with a narcissistic personality disorder because he had a grandiose sense of self-importance.

Jerad was what psychologists refer to as a grievance collector. He was angry about everything from pollution to politics, gun restrictions to drug laws. And he went to great lengths to voice his anger. He recorded a disturbing YouTube video with him dressed as The Joker from the Batman series to highlight his anger to the world. “This video showed his level of intensity, that he would go to great lengths with make-up and costuming to air his grievances,” said Gaskamp.

While the video indicates an overly narcissistic personality, Gaskamp noted that Jerad’s behavior was not yet concerning. In the video, he is still trying to change the way people think and doing so through non-violent, albeit passionate, means. This video has hints of humor, which is something that is not displayed in later videos as Jerad becomes more enraged. A lack of humor is one small indication of Jerad’s personality shift and his movement toward more serious means of communicating his points.

His wife, Amanda, was 22 years old. Her father suffered from alcohol and meth addictions. She did not have any criminal background and had stayed out of trouble for most of her life. She was a high school graduate and considered creative and obedient by those who knew her. However, she was a very insecure and dependent person. Psychologists noted that she displayed characteristics of person with a borderline personality disorder and dependent personality disorder. Amanda adopted the grievances of Jerad and became a loyal follower.

Indicators Leading to the Attack

As part of Jerad’s self-centered personality, he very easily suffered from what Gaskamp referred to as a narcissistic injury. There were several incidents where Jerad was enraged for what he perceived as being unfairly targeted by police. He was pulled over for road rage and found to have marijuana and pills on him. Soon after this incident, his stepfather called the police because he made threats against his wife, Amanda. Jerad served a short stint in jail and after he got out, he posted messages about wanting to kill police officers on his Facebook account. Such behavior indicates that his grievances against law enforcement escalated, said Gaskamp.

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Gaskamp discussed two types of violent behavior: affective violence and predatory violence. Affective violence is when there is a lot of emotion involved — someone who is considered a hothead who flies off the handle due to emotional triggers. This type of violence is defensive in nature. Predatory violence is the more concerning type of violent behavior and the one that behavioral specialists are trying to predict, said Gaskamp. This is when there is a minimal amount of emotion displayed and allows individuals to plan a violent attack or deliberate retribution at a future time.

Warning Behaviors and Signs of Mass Shooters

Gaskamp discussed the five indicators leading to violent acts.

  1. Pathway: Often starts with a grievance and provides individuals a motive. As a person moves along the pathway to violence, they display more visible behaviors. They move from thought to action via grievance, ideation, research/planning, preparation, breach (i.e. dry run) and finally attack. In this case, it took a year and a half for Jerad to move through these phases.
  2. Fixation: Individuals often have a fixation on a grievance and have little else in their life to distract them. In Jerad’s life, there weren’t a lot of positive things happening. He didn’t have a job, wasn’t attending school and didn’t have many friends.
  3. Identification: Those who did know Jerad said he didn’t just believe the things he ranted about, he became all-consumed by them. All he did was talk about these grievances and would not talk about anything else. These topics became part of his identity.
  4. Leakage: As individuals move towards violence, they start communicating with others about the actions they’re going to take. Jerad posted on his Facebook account about looking to buy a gun.
  5. Last Resort: Right before the shooting, Jerad and Amanda started selling all their possessions. They sold their truck, gave away their cat and pawned their most precious belongings. This is the most concerning stage and an indicator that violence is imminent.

How to Identify and Stop Mass Shooters

“Bystanders are the key to prevention,” said Tillman. But, unfortunately, bystanders don’t always take action. “Some people don’t know what they’re seeing when they see a threat and some don’t want to do the right thing. Those are the barriers we must overcome,” she said.

There are four groups of bystanders: family, peers, authority figures and strangers. Each violent attack has an average of three bystanders. According to BAU’s research, 84 percent of violent attacks had bystanders who had knowledge of that person’s intentions. Of them, 50 percent did nothing to intervene.

Family Members

In such cases, 43 percent of family member bystanders observed troubling behavior of an individual. However, family members are highly resistant to report such behavior. In this case, Jerad’s stepfather actually did file a police report after observing concerning changes in Jerad’s personality and social media posts. However, no other bystanders notified authorities and some of Jerad’s other family members, who held anti-government beliefs themselves, encouraged his rants.


In violent cases, 41 percent of peers see behavior and many observe the mass shooters’ most severe behavior. Many are also aware the person is planning an attack. However, this group is the least likely to intervene and not inclined to report behavior. In Jerad and Amanda’s case, they were reclusive and had a very small peer group toward the end. However, some people did notice behavioral changes. Amanda’s coworkers at Hobby Lobby said she was once extroverted and social, but in recent months had become withdrawn.

Authority Figures

In violent cases, only 11 percent of authority figures observe changing behaviors. They are less likely to report behaviors, but they are also less likely to observe less severe behaviors.


Very few strangers report behavior of others because they often do not have proper context. In this case, there were several strangers who could have reported troubling behavior, including the pawn shop clerk and YouTube followers who had watched Jerad’s increasingly disturbing videos.

Takeaways from This Case

There were several behavioral warning signs that Jerad and Amanda were becoming increasingly unstable individuals. Jerad’s videos, social media posts and conversations became increasingly angry and irrational. Amanda became more withdrawn and dependent on Jerad. While none of these single characteristics or behaviors is enough to indicate instability, the combination is enough to cause concern.

Read about other presentations from INLETS:

Leischen Kranick is a Managing Editor at AMU Edge. She has 15 years of experience writing articles and producing podcasts on topics relevant to law enforcement, fire services, emergency management, private security, and national security.

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