(NewsNation) — The person whom police say opened fire Monday at a Nashville elementary school is part of a short list of gunwomen responsible for shootings that killed or injured multiple people.

On Monday, a shooter killed three children and three adults at the private Christian Covenant School in Nashville.

At a news conference Monday afternoon, police said the shooter identified as transgender. Authorities have publicly identified the suspect, now deceased, as Audrey Hale, a 28-year-old female who previously attended the school. 

A female multi-victim shooter is a rare occurrence. Since 1982, less than 3% of “mass shooters” as defined by the progressive magazine Mother Jones have been female, including Monday’s incident.

For its tracking and reporting purposes, Mother Jones defined a “mass shooting” as a “a single attack in a public place in which four or more victims were killed” — a definition they adopted from the FBI.

The publication expanded its criteria from 2013 onward to include incidents where three or more people died, following a new mandate for federal investigations.

Notably, the first high-profile school shooting in the United States was carried out by a teenage girl in 1979, predating Mother Jones’ research.

Multi-victim shootings at hands of women and girls have remained a rarity since then. Of the 142 cases that Mother Jones examined, just four involved female shooters. Monday’s tragedy was the only one to take place at a school.

Two of the remaining cases happened at the shooters’ places of work. The third took place at a Native American headquarters in Northern California.

The non-partisan, nonprofit group The Violence Project similarly reported that 98% of “mass public shooters” are men. The nonprofit defines a “mass public shooting” as “a multiple homicide incident in which four or more victims are murdered with firearms — not including the offender(s) — within one event, and at least some of the murders occurred in a public location.”

It’s unclear exactly why men more often than women carry out multi-victim shootings, but theories do exist.

“Most mass shootings are spurred by: feelings of pain, anger, humiliation, shame, revenge, desire to make a name for themselves,” said Ellen deLara, an associate professor at Syracuse University told NewsNation in an email Monday. “Some are inspired by adherence to outlying groups and religions.”

Men also generally have greater access to guns and feel more comfortable with them, she said.

According to NPR, researchers have said men are more likely to “externalize their problems and look for others to blame, which can translate into anger and violence.”

The Violence Project President Jill Peterson also told NPR that perpetrators often serve as a model for another potential male shooter who might “see themselves” in the previous gunman.