The stereotype of a mass shooter is a white male with a history of mental illness or domestic violence. While that may be anecdotally true, the largest single study of mass shooters ever conducted by the U.S. government has found that nearly all mass shooters have four specific things in common.

A new Department of Justice-funded study of all “mass murder” — killings of four or more people in a public place — since 1966 found that mass shooters typically have an experience with childhood trauma, a personal crisis or specific grievance, and a “script” or examples that validate their feelings or provide a roadmap. And then there’s the fourth thing: legal access to a firearm.

The root cause of mass shootings is an intensely partisan debate, with one side blaming mental health and the others blaming guns. Researchers hope that the findings in the study could usher in a more holistic and evidence-based approach to the issue — and provide opportunities for policy action.

“Data is data,” said Jillian Peterson, a psychologist at Hamline University and co-author of the study. “Data isn’t political. Our hope is that it pushes these conversations further.”

The study, compiled by the Violence Project, a nonpartisan think-tank dedicated to reducing violence in society, was published Tuesday and is the most comprehensive and detailed database of mass shooters to date, coded to 100 different variables. Its release comes less than a week after a teenage boy killed two students at his high school in Santa Clarita, California, before shooting himself in the head.

The researchers used the FBI’s definition of a “mass murder”: four or more people killed in one public place, excluding the shooter. The dataset stretches back to August 1, 1966, when a former Marine opened fire from an observation deck at the University of Texas, killing 15 people. It wasn’t the first mass shooting in the U.S., but researchers chose it as a starting point because it was the first to be substantively covered on radio and TV.

The database delivers a number of arresting findings. Mass shootings are becoming much more frequent and deadly: Of the 167 incidents the researchers logged in that 53-year period, 20% have occurred in the last five years, and half since 2000.

They’re also increasingly motivated by racial, religious, or misogynist hatred, particularly over the past five years.

And in an era when tightening gun laws, including background checks, is a national political issue, the study found that more than half of all mass shooters in the database obtained their guns legally.

But researchers said that they were particularly struck by how many mass shooters displayed symptoms of being in some sort of crisis prior to the shooting. “Those are opportunities for prevention,” said Peterson.

5 profiles of mass shooters

Experts have long cautioned that there is no single profile for a mass shooter. But the Violence Project researchers found some personal characteristics often align with certain types of locations targeted by shooters, and created five general categories::

K-12 shooters: White males, typically students or former students of the school, with a history of trauma. Most are suicidal, plan their crime extensively, and make others aware of their plans at some point before the shooting. They use multiple guns that they typically steal from a family member.

College and university shooters: Non-white males who are current students of the university, are suicidal, and have a history of violence and childhood trauma. They typically use legally obtained handguns and leave behind some sort of manifesto.

Workplace shooters: Forty-something males without a specific racial profile. Most are employees of their targeted location, often a blue-collar job site, and have some grievance against the workplace. They use legally purchased handguns and assault rifles.

Place of worship shooters: White males in their 40s, typically motivated by hate or domestic violence that spills out into the public. Their crimes typically involve little planning.

Shooters at a commercial location (such as a store or restaurant): White men in their 30s with a violent history and criminal record. They typically have no connection to the targeted location and use a single, legally obtained firearm. About a third show evidence of a “thought disorder,” a term for a mental health condition, like schizophrenia, that results in disorganized thinking, paranoia or delusions.

Hate on the rise

The study shows that the number of shooters who are motivated by racism, religious hate and misogyny have increased since the 1960’s — most dramatically in the last five years.

Since 2015, hate-fuelled shootings targeting black churchgoers in Charleston, Jews at synagogues in Pittsburgh and Poway, women at a yoga studio in Tallahassee, and Latinos at a Walmart in El Paso, have dominated national headlines and added another layer of complexity to the problem of mass violence in America.

Between 1966 and 2000, there were 75 mass shootings. Of those, 9% were motivated by racism, 1% by religious hatred, and 7% by misogyny. Of the 32 mass shootings that have occurred in the U.S. just since 2015, 18% were motivated by racism, 15% by religious hatred, and 21% by misogyny.

The increase in ideologically-motivated mass shootings has coincided with the emergence of a newly-emboldened far-right, who’ve forged national and even international alliances of hate online. The sharp rise in misogyny-inspired shootings also squares with the rise of the “Incels,” short for “involuntarily celibate,” an online subculture comprised of angry young men who deeply resent and blame women for their isolation.

Mental health is a factor — but rarely the cause

Two-thirds of the mass shooters in the database had a documented history of mental health problems. While this seems high, researchers point out that roughly 50% of Americans have experienced some kind of mental health problem at some point in their lives.

Moreover, the percentage of shooters whose crimes were directly motivated by the symptoms of a mental disorder (such as delusions or hallucinations caused by psychosis) is much smaller: roughly 16%. That is a smaller percentage than shooters motivated by hate, a workplace grievance, or an interpersonal conflict.

“If someone has a mental health history, I think we’ve gotten in the habit of blaming that for their actions,” said Peterson. “But someone can have, say, depression, and it’s not like everything they do is driven by that.”

That said, the study found strong links between suicidal motivations and mass shootings. Nearly 70% of shooters were suicidal before or during the shooting, and the numbers are even higher for school shooters.

These findings could have powerful implications for public policy, according to the researchers. “This shows us that there are opportunities for intervention — this doesn’t just happen out of the blue,” Peterson said.

“We know a lot more about suicide prevention than we do about this issue, and we know what works — things like limiting access to weapons, directly asking the question, connecting people with outside resources, not talking about it in the news.”

Seeking out fame

The percentage of shooters driven by a desire for fame has risen substantially in the last five years, the study found. In the first 15 years of the 21st century, some 3% of perpetrators were motivated by the desire to go down in history as a mass shooter.

Between 2015 and 2019, that number jumped to 12%.

One specific motivator for fame-seekers remains strangely persistent through the years: the Columbine High School massacre.

There had been many mass shootings and even school shootings before, but Columbine, which took place in 1999 at a public high school in Littleton, Colorado, redefined the school shooting as a media spectacle. The chaotic scene outside the school was broadcast live for several hours before the perpetrators were found to have died by suicide, the shooters left an extensive record of their plans and motives.

Columbine’s influence is so great that the study even found that fame-seeking as a motive for mass shootings was largely confined to the American West: 70% of fame-seeking shootings took place in the region. (By comparison, the researchers found no mass shootings in the Northeast directly motivated by fame-seeking.)

How they got their guns

Nearly half the mass shooters in the database purchased their gun legally. Thirteen percent obtained their gun via “theft,” which includes borrowing from friends or family members. School shooters — overwhelmingly young — were most likely to acquire their guns in this manner. Researchers said that this particular data point could bolster arguments for legislation requiring safe storage of firearms.

Handguns were by far the most common firearm used in mass shootings, and were used three times the rate of shotguns, rifles, or assault rifles.

Assault rifles were banned in 1994 during the Clinton Administration, but the federal ban expired a decade later and gun manufacturers pounced on the opportunity to re-market military-style firearms to civilians.

Researchers said that there had been a statistically significant increase of assault rifle use in mass shootings in the last five years, which has also coincided with shootings becoming more deadly.

Cover: Mourners gather at a vigil held for shooting victims on November 17, 2019 in Santa Clarita, California. Nathaniel T. Berhow, a 16 year-old-student, died from a self-inflicted gunshot wound after killing two people and injuring three others in the November 14th shooting at Saugus High School in Santa Clarita. (Photo by Apu Gomes/Getty Images)