A prayer service on Saturday evening at St. Pius X Catholic Church in El Paso, TexasCelia Talbot Tobin / ​The New York Times / Redux

Updated at 1:43 p.m. on August 5, 2019.

The man accused of killing 22 people and injuring dozens more at a Walmart in El Paso, Texas, this weekend was an “extreme loner” who was “picked on” for his voice and his clothes, the Los Angeles Times reported.

The lonely life of the suspect, who is widely reported to be 21-year-old Patrick Crusius of Allen, Texas, reveals a troubling pathway to violence for some terrorists, including mass shooters. Feeling alienated from their peer groups, they seek vengeance in the most dramatic—and deadliest—way possible.

Of course, not all mass shooters were bullied as children. The Columbine High School killers, for example, had healthy friend groups. And some shooters were more the bullies than the bullied: The man who is suspected of killing nine in Dayton, Ohio, hours after the El Paso attack was also reported to have kept a “kill list” and “rape list” of his high-school classmates.

But there are nevertheless clear links between loneliness, social exclusion, and the kind of radicalization that leads to violence. A 2004 study found that nearly three-quarters of school shooters had been bullied or harassed. In another study, bullying victims who also experienced fighting, threats, or injury, or who skipped school out of fear, were significantly more likely to carry weapons to school compared with kids who weren’t bullied. A study of 15 school shootings from 1995 to 2001 found that “acute or chronic rejection—in the form of ostracism, bullying, and/or romantic rejection—was present in all but two of the incidents.” Though the El Paso shooter targeted a Walmart, not a school, his severe angst and dark motives appear similar to those of many school shooters.

Rejection alone, of course, is not enough to cause violence. The authors of the studies on bullying typically point to additional factors that convert the sting of rejection to the horror of homicide. The shooters tend to have psychological problems, for example, and have little support for dealing with them. They are fascinated by guns and have little empathy for others.

Also writing in the Los Angeles Times this weekend, the researchers Jillian Peterson and James Densley described several commonalities that they’ve identified among mass shooters. The majority of mass shooters in their study experienced childhood trauma, sometimes including severe bullying, before reaching a “crisis point” involving a specific grievance, such as a romantic rejection. Most shooters also studied the acts of other terrorists: A manifesto that officials believe was written by the El Paso suspect praised the man who killed 51 people in Christchurch, New Zealand, earlier this year.

This line of research isn’t specific to American-born mass shooters. For instance, one study found that Muslim immigrants who felt marginalized and insignificant were more supportive of radical beliefs and a hypothetical fundamentalist group. Like school shooters, they showed a desire for vengeance, and a need to get back into a group’s warm embrace—even if that group is a club of extremists and mass murderers.

“Analyses of political radicalization or school shootings consider these as extreme consequences of the individual’s desire to get back at the group that excluded them,” the psychologist Naomi Ellemers wrote in Science in 2012.

In the past, media coverage of mass shootings has focused almost exclusively on the bullying the perpetrators experienced, sometimes problematically obscuring the cultural or political influences that may have led shooters to act. The role that anti-immigrant sentiment played in the El Paso attack shouldn’t be ignored. And in the end, all the bullying, rejection, and hatred in the world can’t become deadly without the fourth factor Peterson and Densley found in their analysis: the means to carry out deadly plans. That is, the gun. “In 80 percent of school shootings,” they write, “perpetrators got their weapons from family members, according to our data. Workplace shooters tended to use handguns they legally owned. Other public shooters were more likely to acquire them illegally.”

America’s is not a uniquely cruel culture, but it is a culture awash in guns. While bullies exist everywhere, the United States has one of the highest gun-ownership rates in the world. That’s what makes social rejection in this country so uniquely deadly.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.