It’s been decades since a teenage girl was at the center of a mass school shooting investigation involving multiple dead, according to the Twin Cities experts who created a massive, comprehensive nationwide database of mass shooters.

Of 349 homicides at U.S. K-12 schools since 2000, 12 of the known shooters were females — nine of whom were teenage girls under 18, according to the data compiled by Hamline University’s Violence Prevention Project Research Center. That’s less than 3%.

The 15-year-old girl suspected of opening fire in a study hall classroom at Abundant Life Christian School on Monday morning would be the tenth female juvenile school shooter in nearly 25 years.

Further, Monday marked the first time in 45 years that a juvenile female shooter allegedly took multiple lives on school grounds, said Violence Project Research Center Co-Founder James Densley.

The last was in 1979 when 16-year-old Brenda Spencer shot 11 people, killing two, at a San Diego elementary school.

Although the statistic is rare, the circumstances surrounding the Madison shooting were not, Densley emphasized.

“If we step back, we see the same story repeated again and again. A student insider. In crisis. Suicidal. With access to a gun,” he said.

“More than 90% of school mass shooters show clear signs of a crisis…” and just as many “leak their plans ahead of time.”

Madison Police on Tuesday said a “combination of factors” likely motivated suspect Natalie “Samantha” Rupnow to carry out the shooting, allegedly killing a teacher and a fellow student before turning the gun on herself.

Six other students were hurt, two of them were still fighting for their lives as of Tuesday, Madison Police Chief Shon Barnes said.

“There are always signs of a school shooting before it occurs,” he said during the latest press briefing.

Chief Barnes did not share what those possible signs were as investigators continued to work through evidence from the suspect’s home and verify online rumors.

“We’re looking into her online activity. We’re asking anyone who knew her or may have insight into her feelings leading up to yesterday to please contact the Madison area Crimestoppers,” the Chief said.

Former FBI Special Agent Kyle Loven has worked a few mass shooting cases in his career, but never one involving a young female shooter, he said.

“Within the context of mass shootings, it’s amazingly rare,” he shared in an interview on Tuesday.

“A lot of these types of issues and pressures and mental illness, a lot of these factors all come into play. And I don’t think they’re found in just one gender,” he continued.

“But as far as why these characteristics, or why these propensities, are primarily found with male shooters, I’m not sure there’s a clear-cut answer for that.”

Madison Mayor Satya Rhodes-Conway noted on Tuesday that the city created an online resource page where community members can turn for mental health support and other services. It’s also the place to for anyone interested in finding out how to help support affected families, she said.