It has been a quarter-century since the massacre at Columbine High School.
On April 20, 1999, two teenage gunmen shot and killed 12 students and a teacher in Littleton, Colorado, before turning their guns on themselves.
It ushered in the modern era of school shootings, and polls ever since have captured the fears of many parents that their children are in danger when they go to school.
In those 25 years, the number of people killed with guns on school property has climbed to least 493, David Riedman, the creator of the K-12 School Shooting Database, told Newsweek. At least 138 of those people were killed in active shooter incidents on school grounds.
But determining exactly how many “school shootings” have occurred in the U.S. since Columbine is complicated. It depends on how the term is defined—and can range from just eight to more than 2,000.
The K-12 School Shooting Database uses an inclusive definition that includes any incident when a gun has been brandished, fired or when a bullet has hit school property, regardless of the number of victims, time, day, or reason.
Using that criteria, there have been at least 2,032 school shootings since Columbine—and the number of incidents each year has risen dramatically in recent years. There have been 95 incidents so far in 2024, and last year they climbed to a record high 348.
But the number of school shootings since Columbine goes down to 1,143 if the data is filtered to only account for incidents where one or more victims have been shot.
At least 133 of those incidents involved an “active shooter,” defined by Riedman as when the shooter has killed or injured victims, either targeted or random, within the school campus during a continuous episode of violence. Riedman also noted that his research found that the Columbine shooting inspired at least 23 other school shooters.
But if a mass shooting is defined as one where there at least four people have been shot, there have been 59—which excludes some 97 percent of gunfire incidents that have happened on school grounds since Columbine.
School shootings where at least four people have been killed, like the one at Marjory Stoneman Douglas High School in Parkland, Florida, in 2018 and, more recently, at Robb Elementary School in Uvalde, Texas, are even rarer—with only eight such incidents since Columbine.
But “in any of those different ways that you can filter this criteria, there is a trend line that’s going up,” Riedman told Newsweek.
“Each one of those ways that you filter the data tells an important story for different purposes. If you’re a school administrator trying to figure out the whole picture of the problem with gun violence on school property, you care about all 2,000 of those incidents. If you’re somebody who only wants to look at mass fatality attacks,