What We Know About Brian Thompson’s Killer and His Journey Through the Attack Cycle

By Trevor Thrasher

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In my classes on active threat prevention and response, awareness courses for protection agents, and courses for executives and everyday people concerned about crime and violence, I often discuss the Cycle of Violence, also known as the Attack Cycle. This framework outlines the stages that attackers progress through when planning and executing violent acts. Whether it’s a street criminal, a terrorist, or someone preparing a targeted assassination, the cycle remains largely consistent. Understanding these stages helps identify red flags and intervene before a plan escalates into violence.

The December 4, 2024, assassination of UnitedHealthcare CEO Brian Thompson by Luigi Mangione is a chilling illustration of this cycle. Mangione went through each stage—predisposition, grievance, stressors, behavioral change, ideation, triggering event, planning, and execution—with methodical precision. To appreciate how this unfolded, let’s break down the case step by step and examine the opportunities that were missed to prevent it.

Predisposition: High IQ, High Performer, Hidden Pathology

At the beginning of the attack cycle, there is typically a predisposition—a foundation shaped by early life experiences or long-standing psychological traits. These predispositions create a person’s character and make them either prone to committing violence or easily influenced toward violent or criminal behavior. Common predispositions include mental illness, medical issues, childhood neglect or abuse, growing up in broken families or with absentee parents, social isolation, and experiencing poverty.

Mangione’s predisposition is a study in contrasts. He was a valedictorian at the elite Gilman School and earned dual degrees in computer science from the University of Pennsylvania—credentials that should have set him up for success. Yet, he couldn’t hold a stable job; his most recent employment as a data engineer for TrueCar, Inc. ended in 2023. This inconsistency hints at an undiagnosed mental health issue.

I’ve seen this kind of pattern before. There are people with exceptionally high IQs who possess a “glitch.” These individuals can function well, even brilliantly, in society—until something snaps or they simply make a deliberate decision that violence is the answer. A psychologist I encountered during Special Forces selection explained that high-functioning sociopaths can be cold, calculating, and capable of carrying out violent acts with mathematical precision once they’ve made the decision. He explained they apparently make great special operators and, unfortunately, mass murderers.  Sociopaths like this can suppress emotion and act with chilling calmness, which is exactly what Mangione appeared to do. His ability to execute his plan with no hesitation suggests a personality type that could turn lethal when grievances and stressors mounted beyond his breaking point, or simply because it was what he decided he needed to do.

Adding to this predisposition were some reports of chronic back pain worsened by a surfing accident. He described experiencing “intermittent numbness” and “brain fog,” symptoms that often accompany severe back injuries. This kind of chronic pain often leads to the use—or misuse—of prescription opioids or other medications. While it’s speculation at this point, the potential for drug use is something to consider, as it can cloud judgment and exacerbate underlying mental health issues.

Grievance: When Resentment Turns to Rage

Grievances are the fuel that feeds the fire of violent ideation. Mangione’s chronic pain and frustration with medical care transformed into deep resentment toward the healthcare industry and corporate America. In his three-page manifesto, he called health insurance companies “parasitic” and justified his actions by saying, “These parasites had it coming.” He decried a system where corporate profits soared while people like him suffered. The inscriptions on the shell casings found at the crime scene—“deny,” “defend,” and “depose”—reflected his anger at the insurance industry’s claim-rejection tactics.  The specifics of what exactly caused his resentment are still unknown.

While everyone develops some idea of vindictiveness, I have found that three components elevate it to a dangerous level: severely unreasonable resentment; bridging a specific complaint to an entire group or, conversely, irrational laser-like targeting of an individual; and finally, dehumanization.

Mangione’s references to insurance executives as “parasites” show how he no longer viewed his targets as people. This mental shift makes committing violence psychologically easier. Dehumanization isn’t unique to lone attackers; it’s a tactic used in war to justify killing the enemy. Think of all the names our “enemies” have been called and the way they have been characterized as less than human and evil throughout our various wars. When a person’s grievance reaches this level, the risk of violent action increases dramatically.

Stressors and Behavioral Change: The Breaking Point 

Stressors amplify grievances, pushing individuals toward action. Mangione’s back surgery in 2024 was a pivotal stressor that worsened his physical pain and mental state. Following the surgery, he withdrew from friends and family, prompting his family to report him missing in November 2024. This level of isolation was a clear sign that something was wrong. Combined with his inability to maintain employment, these stressors likely deepened his sense of hopelessness and inadequacy.  Secret Service studies show attackers typically suffer multiple high-level stressors in a period of only a year or two.

Behavioral changes like social withdrawal and a decline in communication are classic indicators that someone is struggling. Friends noted they hadn’t heard from Mangione in months. His online presence faded, except for his telling review of Theodore Kaczynski’s manifesto, where he praised the Unabomber as a “political revolutionary.” This type of leakage—subtle hints that someone is considering violence—was present but went unaddressed due to its low-level nature and, as of yet, lack of previous threats.

Ideation and Trigger: When Violence Becomes the Solution

In the ideation stage, the decision to commit violence solidifies. Mangione’s manifesto reveals that he saw his attack as a necessary act of retribution. His admiration for Kaczynski suggests he sought validation for his violent thoughts. The exact trigger remains unclear, but it was likely a culmination of his pain, frustration, and isolation. A final perceived injustice—perhaps related to his medical treatment or other struggles—pushed him from ideation to action.

Planning and Preparation: Cold, Calculated Precision

Mangione’s planning was meticulous. He targeted Thompson outside the UnitedHealth Group investor conference at the New York Hilton Midtown. Arriving just five minutes before the shooting, he demonstrated careful reconnaissance and timing. His weapon choice reflects deliberate preparation. He may have used a ghost gun, a firearm assembled from parts without serial numbers, making it harder to trace. Reports suggest the weapon may have included 3D-printed components. The silencer he used is also notable—legal to obtain with ATF approval but challenging to manufacture or acquire illegally. These choices highlight his technical knowledge and determination to remain undetected.

His escape plan was equally calculated. After the shooting, he fled on an electric bike, disappearing into Central Park. Investigators later found a gray backpack containing a jacket, possibly part of his disguise. This level of planning suggests he rehearsed the attack and the getaway, aiming to evade capture.  Despite his intelligence and planning, plenty of mistakes were made.  But human habits like flirting with a girl, chewing gum, or getting your daily cup of coffee are hard to break. With phone tracking and video cameras everywhere, the murder of a high-profile person has become exponentially harder.  In the spy and special operations world, activities like this require a team to plan and support and a high level of isolation before and during the event.

The Attack: Precision and Calm

On December 4, 2024, Mangione executed his plan with chilling efficiency. He shot Thompson in the back and calf using a silenced pistol. When his gun jammed, he calmly cleared the malfunction and continued firing. His demeanor—cold, detached, and methodical—was that of someone who had committed to his actions long before pulling the trigger.  There was zero hesitancy and behaviorally, he appeared totally unfazed by his act.

Differences Between Attack Cycles

While the attack cycle for active killers, terrorists, and street criminals shares similarities, there are critical differences. Active killers like Mangione often have personal grievances and meticulous planning, but typically lack the broader ideological motives of terrorists. Terrorist attack cycles emphasize target selection that furthers a political or religious agenda, extensive reconnaissance, and often group coordination. Street criminal attack cycles focus on immediate rewards, surprise, and opportunistic strikes, with less planning and more emphasis on avoiding capture.

Mangione’s case sits between the active killer and terrorist profiles. His attack had a personal motive but also a broader ideological grievance against the healthcare system.

Conclusion: Lessons from the Attack Cycle

 Mangione’s progression through the attack cycle highlights the importance of recognizing the warning signs:

 1. Predisposition: High IQ, mental health issues, chronic pain

 2. Grievance: Resentment toward healthcare and corporate America

 3. Stressors: Back surgery, employment struggles

 4. Behavioral Change: Social withdrawal, fixation on grievances

 5. Ideation: Manifesto writing, dehumanization of targets

 6. Trigger: A final perceived injustice

 7. Planning: Ghost gun, silencer, reconnaissance, escape route

 8. Attack: Calculated, cold-blooded execution

Recognizing these patterns, understanding the psychology behind them, and acting on things like leakage can help prevent future tragedies. Staying vigilant could mean the difference between stopping a plan early or witnessing it unfold. 

If you want to learn how to interrupt this cycle and protect yourself and your loved ones from random or targeted attacks, visit my active threat seminar page for live training and seminars.

If you want to threat-proof your family against active threats and other attacks, making them 100% more threat-proof in just a few short 15-minute lessons, check out my Threat-Proof Family guide: here

Be responsible, capable, and confident in a crisis.

Trevor