The person who killed three schoolchildren and three adults at a Nashville Christian school is a 28-year-old who police say once attended the school. The shooter was armed with at least two AR-15 assault-style rifles and died by gunfire when confronted by police.

Besides the sheer horror of another mass shooting, the shooter’s gender sets this incident apart. (Police said late Monday that the suspect in this shooting identified as trans and used male pronouns. They offered no linkage between the shooter’s gender identity and the motivations for the shootings. Poynter’s Kelly McBride offers advice for reporting on the shooting responsibly.) This is data from 1966 through February 2023 from Statista:

(Statista)

Also consider this data from the Rockefeller Institute of Government, which mined data going back to 1966:

(Rockefeller Institute of Government)

The profile of school shooters

In 2019, the Secret Service produced a profile of mass shooters who target schools. That profile used data from 41 K-12 school shootings and found:

• There is no profile of a student attacker, nor is there a profile for the type of school that has been targeted: Attackers varied in age, gender, race, grade level, academic performance, and social characteristics. Similarly, there was no identified profile of the type of school impacted by targeted violence, as schools varied in size, location, and student-teacher ratios.
• Attackers usually had multiple motives, the most common involving a grievance with classmates: In addition to grievances with classmates, attackers were also motivated by grievances involving school staff, romantic relationships, or other personal issues. Other motives included a desire to kill, suicide, and seeking fame or notoriety.
• Most attackers used firearms, and firearms were most often acquired from the home: Many of the attackers were able to access firearms from the home of their parents or another close relative. While many of the firearms were unsecured, in several cases the attackers were able to gain access to firearms that were secured in a locked gun safe or case.
• Most attackers had experienced psychological, behavioral, or developmental symptoms:The observable mental health symptoms displayed by attackers prior to their attacks were divided into three main categories: psychological (e.g., depressive symptoms or suicidal ideation), behavioral (e.g., defiance/misconduct or symptoms of ADD/ADHD), and neurological/developmental (e.g., developmental delays or cognitive deficits).
• Half of the attackers had interests in violent topics 
• All attackers experienced social stressors involving their relationships with peers and/or romantic partners:Attackers experienced stressors in various areas of their lives, with nearly all experiencing at least one in the six months prior to their attack, and half within two days of the attack.
• Nearly every attacker experienced negative home life factors: The negative home life factors experienced by the attackers included parental separation or divorce, drug use or criminal charges among family members, and domestic abuse. While none of the factors included here should be viewed as predictors that a student will be violent, past research has identified an association between many of these types of factors and a range of negative outcomes for children.
• Most attackers were victims of bullying, which was often observed by others: Most of the attackers were bullied by their classmates, and for over half of the attackers the bullying appeared to be of a persistent pattern which lasted for weeks, months, or year.
• Most attackers had a history of school disciplinary actions, and many had prior contact with law enforcement: Most attackers had a history of receiving school disciplinary actions resulting from a broad range of inappropriate behavior.

Mass shootings in U.S. schools

A database from The Violence Project provides an overview of mass public shootings in the United States.

(The Violence Project)

It also dices out commonalities for different mass shooting settings. Vice summarized:

• 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: Fortysomething 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 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.

The AR-15, once again, is the weapon of choice for a mass killer

The killing in Nashville just happens to have occurred as The Washington Post produced new reporting about the history and culture behind the semi-automatic .227 caliber rifle that is often used by mass killers. 10 of the 17 deadliest killings in the United States have involved AR-15s.

(Washington Post)

The Post found:

• Today, the AR-15 is the best-selling rifle in the United States, industry figures indicate. About 1 in 20 U.S. adults — or roughly 16 million people — own at least one AR-15, according to polling data from The Washington Post and Ipsos.
• Almost every major gunmaker now produces its own version of the weapon. The modern AR-15 dominates the walls and websites of gun dealers.

(Washington Post)

• While handguns are involved in the bulk of U.S. gun homicides — responsible for 90 percent of the deaths in cases where details are available, compared to less than 5 percent for rifles, the FBI says — AR-15 sales jump the most with each school shooting and contentious presidential campaign.
• They soared in the run-up to the election of Democrat Barack Obama in 2008 and after the mass killings at an elementary school in Newtown, Conn., in 2012 and a high school in Parkland, Fla., in 2018, and again ahead of the turbulent 2020 presidential election.
• Today, the industry estimates that at least 20 million AR-15s are stored and stashed across the country.

The politics of the AR-15

Gun rights groups often refer to the AR-15 as “modern sporting rifles,” but President Joe Biden uses a phrase that was once part of federal statutes: assault weapons.

Following the Parkland, Florida, shooting at Marjory Stoneman Douglas High School, then-President Donald Trump floated the notion of an assault weapons ban and even mentioned the AR-15 by name. CBS News noted:

In his 2000 book “The America We Deserve,” the president said he supports a ban on assault weapons.

“I generally oppose gun control, but I support the ban on assault weapons and I also support a slightly longer waiting period to purchase a gun,” Mr. Trump wrote at the time.

As a candidate and repeatedly as president, Biden has called for a ban on assault weapons. As a candidate, Biden said but has not accomplished:

Ban the manufacture and sale of assault weapons and high-capacity magazines. Federal law prevents hunters from hunting migratory game birds with more than three shells in their shotgun. That means our federal law does more to protect ducks than children. It’s wrong. Joe Biden will enact legislation to once again ban assault weapons. This time, the bans will be designed based on lessons learned from the 1994 bans. For example, the ban on assault weapons will be designed to prevent manufacturers from circumventing the law by making minor changes that don’t limit the weapon’s lethality. While working to pass this legislation, Biden will also use his executive authority to ban the importation of assault weapons.

Biden also wanted to:

• Regulate possession of existing assault weapons under the National Firearms Act. Currently, the National Firearms Act requires individuals possessing machine-guns, silencers, and short-barreled rifles to undergo a background check and register those weapons with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). Due to these requirements, such weapons are rarely used in crimes. As president, Biden will pursue legislation to regulate possession of existing assault weapons under the National Firearms Act.
• Buy back the assault weapons and high-capacity magazines already in our communities.  This will give individuals who now possess assault weapons or high-capacity magazines two options: sell the weapons to the government, or register them under the National Firearms Act.
• In order to reduce the stockpiling of firearms, Biden supports legislation restricting the number of firearms an individual may purchase per month to one.

Congress has no interest in these ideas.

Avoid stigmatizing mental health

Mental health is often associated with mass shootings, but avoid stigmatizing mental health. Keep this report by the Columbia University Department of Psychiatry in mind:

The reality is that people with mental illness account for a very small proportion of perpetrators of mass shootings in the U.S., says Ragy Girgis, MD, associate professor of clinical psychiatry in the Columbia University Department of Psychiatry and the New York State Psychiatric Institute.

The public tends to link serious mental illnesses, like schizophrenia or psychotic disorders, with violence and mass shootings. But serious mental illness—specifically psychosis—is not a key factor in most mass shootings or other types of mass murder. Approximately 5% of mass shootings are related to severe mental illness. And although a much larger number of mass shootings (about 25%) are associated with non-psychotic psychiatric or neurological illnesses, including depression, and an estimated 23% with substance use, in most cases these conditions are incidental.

Additionally, as we demonstrated in our paper, the contribution of mental illness to mass shootings has decreased over time.

The data suggest that while it is critical that we continue to identify those individuals with mental illness and substance use disorders at high risk for violence and prevent the perpetration of violence, other risk factors, such as a history of legal problems, challenges coping with severe and acute life stressors, and the epidemic of the combination of nihilism, emptiness, anger, and a desire for notoriety among young men, seem a more useful focus for prevention and policy than an emphasis on serious mental illness, which leads to public fear and stigmatization.

Update: This article was amended to include a line about the shooter’s gender identity.