Police identified the suspect in the shooting at Abundant Life Christian School in Madison as Natalie Rupnow, a student at the school who went by the name Samantha.
After allegedly killing a teacher and a classmate, and leaving five others injured, including two students in critical condition, Rupnow died from a self-inflicted gunshot wound, according to police.
"It's a very sad but a rare thing to have a female school shooter," said Don Mihalek, a retired senior special agent for the Secret Service and an ABC News contributor. "Historically, and the studies show, that typically it's a white male student or former student that ends up committing these acts of violence in schools."
The U.S. Secret Service National Threat Assessment Center (NTAC) studied 41 incidents of targeted school violence incidents between 2008 and 2017, including those where no one was injured, and found that 83% of the suspects were male and 17% were female.
Another study by the FBI found that of the 49 shooters involved in 48 active shooting incidents in the United States in 2023, 98% were male.
Among the perpetrators who committed school shootings in 2023 was 28-year-old Audrey Hale, who killed three students and three staff members at the Covenant School in Nashville, Tennessee, where authorities said she was once a student. Hale owned seven firearms, including three used in the shooting at the private school, according to police. Officials said that Hale was being treated for an unspecified emotional disorder. Hale was killed on the scene by two officers.
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A police spokesperson told ABC News that Hale was assigned female at birth and pointed to a social media account linked to Hale that included the use of the pronouns he/him.
An FBI review of 345 suspects involved in 333 active shooting incidents between 2000 and 2019, including 62 that occurred in educational environments, 332 were male and 13 were female.
The Gun Violence Archive, a website that tracks all shootings in the United States, found that of the 805 school shooting incidents since 2012, 157 involved female "participants."
The National Center for Education Statistics also found that 94% of the active shooters in education settings between 2000 and 2022 were male.
Madison police investigators have not yet suggested a motive for Monday's school shooting nor have they said whether the victims were specifically targeted.
The suspect's parents are cooperating with the investigation, Madison Police Chief Shon Barnes told ABC News.
Students in kindergarten through 12th grade attend the Christian school. Police said the shooting was contained to "a classroom in a study hall full of students from multiple grade levels."
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Police have also yet to say where the suspect got her hands on the handgun used in the shooting.
"In almost all of these situations, the students that have access to weapons have generally accessed them from parents, family," Mihalek said.
Mihalek said one of the few female active shooters in recent years that he could recall was Portia Odufuwa, then 37, who opened fire inside Dallas' Love Field Airport in 2022 before she was shot and wounded by police. No one else was injured in the shooting and Odufuwa was found not guilty by reason of insanity in 2023 on charges of aggravated assault.
Other female active shooters include Jennifer San Marco, a former U.S. Postal employee who in January 2006 shot and killed six people at a mail processing and distribution center near Santa Barbara, California, after killing her neighbor, according to police. San Marco died from suicide.
In 2015, Tashfeen Malik, 29, and her husband, Syed Rizwan Farook, 28, who had both pledged support for ISIS, fatally shot 14 people at a December 2015 holiday party in San Bernardino, California. Malik and Farook were killed in a shootout with police.
Mihalek said investigators are likely combing through the social media footprint of the suspect in the Wisconsin school shooting as they search for a motive.
"I think there's a lot of stuff on social media that is creating these mental health crises within kids, especially girls," Mihalek said. "Now, instead of finding your self-worth in good grades, doing well on a sports team, playing a musical instrument well, teachers and parents telling you 'good job,' it's how many likes, how many people are viewing your feed."
Mihalek said that a lot of girls have been the victims of online bullying.
"It's tearing apart a kid's fabric and a lot of them don't know how to handle it because they're not really capable at these young ages to understand how to handle a bullying incident like that," Mihalek said. "In all schools, the key is homing in on behaviors and the pathways to violence. The critical behaviors that put kids on a pathway to violence are social stressors and grievances. If you're being cyberbullied and told you're no good online by multiple people, that can easily become a grievance."
ABC News' Jack Date and Briana Stewart contributed to this report.