Any consideration of new or existing gun laws that follows mass shootings is likely to generate requests for comprehensive data on the prevalence and deadliness of these incidents. In 2015, the Congressional Research Service produced Mass Murder with Firearms: Incidents and Victims, 1999-2013 (July 30, 2015 R44126). Additional sources, an admittedly eclectic sample, include the following:

• FBI’s’ Supplemental Homicide Reports
• Mother Jones’ A Guide to Mass Shootings in America
• US Mass Shootings, 1982-2017: Data From Mother Jones’ Investigation
• Statista’s Number of victims of the worst mass shootings in the United States between 1982 and October 2017 and
• Statista’s Number of mass shootings in the United States between 1982 and October 2017, by shooter’s race and ethnicity

For background, see also Grant Duwe, Mass Murder in the United States: A History (McFarland, 2007) This book examines 909 mass murders that took place in the United States between 1900 and 1999. By far the largest study on the topic at the time, it begins with a look at the patterns and prevalence of mass murders by presenting rates and by describing the characteristics of mass killers. Placing the phenomenon within the broader social, political, and economic context of the twentieth century, the work examines the factors that have influenced trends in the prevalence of mass murder. — Joe