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Understanding the Mass Shooting Database

While media outlets and organizations differ in how they define mass shootings, the Everytown for Gun Safety Support Fund defines mass shootings as incidents in which four or more people are shot and wounded or killed, excluding the shooter. However, this database currently captures shootings with five or more casualties because of how infrequently media and police reports identify the recovered weapons. To learn more about mass shootings and their devastating impact on Americans, click here.

For each listing, we’ve attempted to label the guns that were used, or recovered by law enforcement at the scene of the shooting, by make, model, caliber, and type. We’ve also indicated if the firearms are considered assault weapons, either in stock configuration or as used by the shooters. We define assault weapons as semi-automatic rifles, pistols, and shotguns that accept detachable magazines and possess certain military-style features, as outlined by the 1994-2004 federal assault weapons ban, current state laws, and the federal assault weapons ban that the U.S. House of Representatives passed in July 2022

Similarly, when possible, we’ve indicated if the weapons were designed to accept high-capacity magazines or were used with them. We define high-capacity magazines as those that hold over 10 rounds of ammunition, as adopted by federal and state laws.

To learn more about assault weapons and high-capacity magazines, click here.

We strive for accuracy, and the information was compiled using news reports, police records, photographs, and other publicly available documents, as indicated in the “Source” column. Each URL listed may provide more information on one firearm or multiple. For questions, comments, or corrections, please email us at