What We Know about Mass School Shootings—and Shooters—in the U.S.

When the Columbine High School massacre took place in 1999 it was seen as a watershed moment in the United States – the worst mass shooting at a school in the country’s history.

Now, it ranks fourth. The three school shootings to surpass its death toll of 13 – 12 students, one teacher – have all taken place within the last decade: 2012’s Sandy Hook Elementary attack, in which a gunman killed 26 children and school staff; the 2018 shooting at Marjory Stoneman Douglas High School in Parkland, Florida, which claimed the lives of 17 people; and now the Robb Elementary School assault in Uvalde, Texas, where on May 24, 2022, at least 19 children and two adults were murdered.

We are criminologists who study the life histories of public mass shooters in the U.S. As part of that research, we built a comprehensive database of mass public shootings using public data, with the shooters coded on over 200 different variables, including location and racial profile. For the purposes of our database, mass public shootings are defined as incidents in which four or more victims are murdered with at least one of those homicides taking place in a public location and with no connection to underlying criminal activity, such as gangs or drugs.