The mass shooting in a church in Sutherland Springs, Texas, on Sunday added 26 deaths to a year of violence across the country, from a Las Vegas concert to the Fort Lauderdale, Florida, airport. According to data from multiple sources, shootings like these are claiming more lives than they have at any point in the last 35 years.

Information on mass shootings is notoriously hard to acquire, in part because the federal government does not provide funding for gun violence research. But in the absence of good, up-to-date official government data, other entities have stepped in. The magazine Mother Jones, for example, keeps a database of all incidents where four or more victims are killed in a public space, excluding deaths that came as part of crimes like a robbery or gang violence.

These criteria are based on the FBI’s own definition of a mass shooting. While the FBI changed its definition of a mass shooting in 2013 to include incidents where three or more victims were killed (and Mother Jones followed suit), in order to maintain consistency, we considered only incidents in this database in which four or more people were killed.