The latest mass shooting that left at least 16 people dead and dozens injured in Lewiston, Maine, added to a list of 565 reported across the United States this year, according to the Gun Violence Archive.

The nonprofit and CNN define mass shootings as those in which four or more people are shot, excluding the shooter.

Nearly 1 in 5 US adults have had a family member killed by a gun, including homicides and suicides, according to a 2023 survey from KFF (formerly known as the Kaiser Family Foundation). About the same proportion of adults have been personally threatened with a gun, and about 1 in 6 adults has witnessed an injury from a shooting, the survey found.

More background: The FBI defines “mass murder” as the murder of four or more people and tracks “active shooter incidents,” but there is no federal or agreed-upon definition for a mass shooting.

For all its data background, the Gun Violence Archive’s work is, at its heart, basic journalism.

Researchers scrape data automatically from about 7,500 law enforcement agencies, media outlets and more organizations, the executive director Mark Bryant told CNN in 2022. They then comb through the results, double-check media sources, follow up with police, and add that information to the database. Most shootings are added to the system within about 72 hours, Bryant said.

CNN's Annette Choi, Eric Levenson and Curt Merrill contributed reporting to this report.