Female assailants in mass shootings in the United States — like the one that occurred on Monday in Nashville — are extremely rare, according to the Violence Project, which maintains a national database of mass shootings dating to 1966.
In a data set of 172 mass shootings, defined as involving four victims or more and collected before Monday’s case, only four assailants were women or girls. In two cases, women acted alongside a man.
The rarity of female aggressors in mass shootings reflects a broader trend: Between 80 and 90 percent of all offenders in homicide cases in any given year are men, according to the Violence Project.
“The female issue is amazingly rare,” said Robert Louden, a retired New York City police officer and a professor emeritus of criminal justice at Georgian Court University, in Lakewood, N.J.
Female offenders in homicide cases are often associated with domestic violence, Professor Louden said.
“Women do kill somebody who had been an abuser,” he said, adding: “Women do not kill or shoot or hold hostages as much as men do. It’s few and far between.”
The archetypical mass shooter is young and male.
Six of the nine deadliest mass shootings in the United States since 2018 were by people who were 21 or younger, representing a shift for mass casualty shootings, which before 2000 were most often initiated by men in their mid-20s, 30s and 40s.
An F.B.I. study of 160 “active shooter” episodes between 2000 and 2013 found that only six, or 3.8 percent, involved female assailants.
In more recent years, there have been several high-profile outliers to the trend of mass shootings committed by young, male gunmen.
In May 2021, a sixth-grade girl brought a gun to her Idaho middle school and wounded two students and a custodian before she was disarmed by a teacher. The shooter, who was not identified because she was a minor, was sentenced to a juvenile corrections center.
In April 2018, Nasim Najafi Aghdam, who the police said was in her late 30s, walked into YouTube’s corporate headquarters in San Bruno, Calif., on the northern edge of Silicon Valley, and opened fire, wounding three people before killing herself. The police said Ms. Aghdam’s anger over what she believed to be unfair treatment by YouTube had set her on a 500-mile drive from her home near San Diego to YouTube’s offices.
