On Monday morning, shots rang out at Abundant Life Christian School in Madison, Wi. leaving one student, a teacher, and the shooter dead with multiple others injured. While school shootings have become all too common in the U.S. one fact sets this one apart: the shooter was a woman.

Fifteen-year-old Natalie Rupnow, found dead on the scene, joins a short list of female shooters who inflict mass violence and who target schools.

“Ninety-five percent of mass shootings are committed by men,”James Alan Fox, a Northeastern University criminologist, told Northeastern Global News. “The overall majority of violent crimes — particularly homicide and gun homicide — are committed by men.”

According to the Mass Killings Database, which breaks down data on mass killings in the U.S., since 2000 there have been 349 homicides in American K-12 schools. Of those shooters, only 12 of them are female, and only nine were girls under the age of 18.

In part, Fox says a major distinction that may contribute to the vast margin in statistics is how these genders approach violence. For one, many of the cases involving female perpetrators involve family.

“Women tend to use violence as a self-defense mechanism to deal with threats that they feel against them,” Fox told Northeastern Global News. “Men oftentimes use violence as an offensive weapon — to establish control.”

Additionally, NPR has reported over the years that many experts believe that there are more male mass shooters than women because men are more likely to place blame outwards, rather than on themselves, which could translate to anger and hostility.

“Some research supports the idea that males are more likely than females to develop negative attributions of blame that are external in nature, that is: ‘The cause… of my problems is someone else or some force outside of me,’” former director of the School of Criminology and Criminal Justice at the University of Nebraska, Omaha Candice Batton, told NPR in 2013.

While a teenage girl inflicting mass violence at her school is rare, the circumstances surrounding this case fall in line with a pattern evident in other instances of school shootings.

“If we step back, we see the same story repeated again and again. A student insider. In crisis. Suicidal. With access to a gun,” Violence Project Research Center Co-Founder James Densley told KTSP.

According to Densley, over 90% of school mass shooters show clear signs of a crisis leading up to the shooting, and just as many leak their plans ahead of time.

The Violence Project’s research has uncovered a common pathway to violence among school shooters, revealing that 73% had a known history of childhood trauma and 92% were suicidal prior to or during the shooting. Additionally, in most cases, access to weapons came through family or friends, with 58% of school shooters obtaining firearms from someone they knew who hadn’t secured them properly. These patterns persist regardless of the shooter’s gender, suggesting that while female perpetrators may be rare, the underlying factors that lead to school shootings remain consistent.

On Wednesday, CNN reported authorities were investigating the authenticity of a document circulated online which is being pegged as the shooter’s manifesto. Additionally, her social media is being investigated for interest in neo-Nazi ideology and involvement in online forums revering mass shooters.