By William Krouse and Daniel J. Richardson

In the wake of tragedy in Newtown CT, Congress defined “mass killings” as “3 or more killings in a single incident” (P.L. 112-265). 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. Despite the pathos of mass shootings, only a handful of researchers and journalists have analyzed the principal source of homicide data in the United States—the Supplementary Homicide Reports (SHR) compiled by the Federal Bureau of Investigation (FBI)—to determine whether those incidents have become more prevalent and deadly. According to the FBI, the term “mass murder” has been defined generally as a multiple homicide incident in which four or more victims are murdered, within one event, and in one or more locations in close geographical proximity. Based on this definition, for the purposes of this report, “mass shooting” is defined as a multiple homicide incident in which four or more victims are murdered with firearms, within one event, and in one or more locations in close proximity. Similarly, a “mass public shooting” is defined to mean a multiple homicide incident in which four or more victims are murdered with firearms, within one event, in at least one or more public locations, such as, a workplace, school, restaurant, house of worship, neighborhood, or other public setting. This report analyzes mass shootings for a 15-year period (1999-2013). CRS analysis of the FBI SHR dataset and other research indicates that offenders committed at least 317 mass shootings, murdered 1,554 victims, and nonfatally wounded another 441 victims entirely with firearms during that 15-year period. The prevalence of mass shooting incidents and victim counts fluctuated sporadically from year to year. For the period 2007-2013, the annual averages for both incidents and victim counts were slightly higher than the years from 1999-2007.

Washington, DC: Congressional Research Service, 2015. 51p.

Edited by Rajeev Ramchand, Jessica Saunders

This report, part of RAND's Gun Policy in America project, presents a collection of essays that synthesize the available scientific data on topics pertinent to firearm policy in the United States. In particular, the authors examine mass shootings, firearm and ammunition taxes, the effects of the 1996 National Firearms Agreement in Australia, whether mental illness is a risk factor for gun violence, and law enforcement approaches to reduce community gun violence.

Santa Monica, CA: RAND Corporation, 2021. 115p.

By Michael Luca, Deepak Malhotra. and Christopher Poliquin

There have been dozens of high-profile mass shootings in recent decades. This paper presents three main findings about the impact of mass shootings on gun policy. First, mass shootings evoke large policy responses. A single mass shooting leads to a 15% increase in the number of firearm bills introduced within a state in the year after a mass shooting. This effect increases with the extent of media coverage. Second, mass shootings account for a small portion of all gun deaths, but have an outsized influence relative to other homicides. Third, when looking at bills that were actually enacted into law, the impact of mass shootings depends on the party in power. The annual number of laws that loosen gun restrictions doubles in the year following a mass shooting in states with Republicancontrolled legislatures. We find no significant effect of mass shootings on laws enacted when there is a Democrat-controlled legislature, nor do we find a significant effect of mass shootings on the enactment of laws that tighten gun restrictions.

Boston, MA: Harvard Business School, 2019. 59p.

By Vivian S. Chu

As the Internet has become a significant venue for facilitating commercial transactions, concerns have arisen regarding the use of this medium to transfer firearms. This report discusses the sale of firearms and ammunition over the Internet, with a focus on the extent to which federal law regulates such activity. A review of the relevant factors indicates Internet-based firearm transactions are subject to the same regulatory scheme governing traditional firearm transactions. Over the years, this has raised concern about the possibility of increased violation of federal firearm laws, as well as challenges that law enforcement may face when attempting to investigate violations of these laws. A review of the relevant factors also indicates that the sale and transfer of ammunition are not as strictly regulated as firearms, and that these changes came into effect in 1986. Lastly, this report highlights recent legislative proposals, S. 3458 and H.R. 6241, companion measures introduced by Senator Frank Lautenberg and Representative Carolyn McCarthy in the 112th Congress that would affect online ammunition transactions.

Washington, DC: U.S. Library of Congress, Congressional Research Service, 2012. 11p.

By Ralph Larkin. 

On April 20, 1999, two Colorado teenagers went on a shooting rampage at Columbine High School. That day, Eric Harris and Dylan Klebold killed twelve fellow students and a teacher, as well as wounding twenty-four other people, before they killed themselves. Although there have been other books written about the tragedy, this is the first serious, impartial investigation into the cultural, environmental, and psychological causes of the massacre. Based on first-hand interviews and a thorough reading of the relevant literature, Ralph Larkin examines the numerous factors that led the two young men to plan and carry out their deed. Rather than simply looking at Columbine as a crucible for all school violence, Larkin places the tragedy in its proper context, and in doing so, examines its causes and meaning.

Philadelphia: Temple University Press, 2007. 265p.

By Steffen Hurka.

Politicization and Policy Change in Western Europe. While the causes of rampage violence have been analysed thoroughly in diverse academic disciplines, we hardly know anything about the factors that affect their consequences for public policy. This book addresses rampage shootings in Western Europe and their conditional impact on politicization and policy change in the area of gun control. The author sets out to unravel the factors that facilitate or impede the access of gun control to the political agenda in the wake of rampage shootings and analyses why some political debates lead to profound shifts of the policy status quo, while others peter out without any legislative reactions. In so doing, the book not only contributes to the theoretical literature on crisis-induced policy making, but also provides a wealth of case-study evidence on rampage shootings as empirical phenomena.

London; New York: Routledge, 2017. 201p.

By Michael R. Vernick, Jon S., Webster, Daniel W.. “The role of guns in violence, and what should be done, are subjects of intense debate in the United States and elsewhere. But certain facts are not debatable. More than 31,000 people died from gunshot wounds in the United States in 2010….Despite the huge daily impact of gun violence, most public discourse on gun policy is centered on mass shootings in public places. Such incidents are typically portrayed as random acts by severely mentally ill individuals which are impossible to predict or prevent.”

Bloomberg. Johns Hopkins Press (2013) 312p.