Shooting incidents such as the one at Sandy Hook Elementary School in December 2012 and the one at an Aurora, CO, movie theater in July 2012 have focused attention on federal policy issues in the law enforcement, public health, and education arenas, among others. The Congressional Research Service (CRS) has identified 78 public mass shootings that have occurred in the United States since 1983. These shootings have claimed almost 550 lives according to CRS estimates. How does the death toll tied to public mass shootings compare with figures related to the preeminent threat that federal law enforcement has confronted in the last decade? CRS estimates that since the terrible events of September 11, 2001 (9/11), Al-Qaeda-inspired homegrown terrorists have killed 14 people in two incidents in the United States. Since 9/11, according to CRS estimates, 281 people have died in 38 public mass shootings. Arguably, the comparatively low death toll associated with Al Qaeda-inspired incidents at least partly results from a large-scale federal focus on homeland security and counterterrorism efforts. It is important to caution the reader that, while tragic and shocking, public mass shootings account for few of the murders related to firearms that occur annually in the United States. According to the Federal Bureau of Investigation (FBI, the Bureau), in 2011, firearms were used to murder 8,583 people. To provide further context, over the last two decades, the nation has experienced a general decline in violent crime. In 1992, 1.9 million violent crimes were reported, while 2011 saw 1.2 million. In the same period, the national murder rate dropped from 9.3 to 4.7 per 100,000 inhabitants. As a starting point, this report delves into public mass shootings over the last three decades, exploring the nature of this threat. In its broader discussion of related federal public health and safety issues, the report covers selected policy implications in three areas: law enforcement , public health , and education . While mass shootings may occur in a number of public settings, the education realm is one that has generated concern from policy makers, officials, and the public alike—at least since the 1999 shooting at Columbine High School in Littleton, CO. The tragedy at Sandy Hook Elementary has renewed such concerns for many. In this report, discussion of each of these is further broken down into efforts geared toward prevention —actions intended to reduce the likelihood of shootings. preparedness — planning how to cope with potential shootings. response —structured efforts employed to react to an actual shooting. Policy measures that deal with recovery are also discussed within the context of education and public health initiatives. Recovery entails helping institutions, communities, and individuals cope with the aftermath of a shooting. This report is not intended as an exhaustive review of specific federal programs in these areas. Also, this report does not focus on gun violence or writ large, nor does it discuss gun control policies. This report attempts to refine the relatively broad concept of mass shooting (which could potentially involve a wide variety of actors targeting victims for any number of reasons) into a narrower formulation: public mass shootings. This has been done to focus discussion around a number of violent incidents that lie outside of specific crime issues such as terrorism, drug trafficking, gang activity, and domestic violence that have federal policies, law enforcement structures, and laws tailored in many instances to specifically address them. In order to delineate a workable understanding of public mass shooting for this report, CRS examined scholarly journal articles, monographs, and government reports. These sources discussed a variety of terms such as mass murder, mass shooting, mass killings, massacres, and multiple homicide. Definitions of these terms varied with regard to establishing the number of victims or fatalities involved, the weapons used, the motives of the perpetrator, and the timeframes within which the casualties or injuries occurred. This report defines public mass shootings as incidents occurring in re latively public places, involvin g four or more deaths—not including the shooter(s)—and gunmen who select victims somewhat indiscriminately. The violence in these cases is not a means to an end such as robbery or terrorism . Relatively public places. For this report, public mass shootings happen in relatively public circumstances. Such settings can include schools, workplaces, restaurants, parking lots, public transit, or even private parties that include at least some guests who are not family members of the shooter. Tallying Fatalities. Any definition of mass shootings requires a somewhat arbitrary threshold demarcating the number of victims killed per incident. This report's threshold is based on a definition of mass murder offered by the FBI. An important caveat deserves mentioning. A compilation of incidents based on any such arbitrary threshold may fail to adequately describe the universe of incidents to which educators, public health professionals, and law enforcement have to react and for which they have to prepare. One author has stated that gunmen "injure far more victims than they kill; however, they must certainly be considered mass murderers by obvious intentions of their actions." In the critical early moments of a shooting, police, teachers, and rescue personnel do not necessarily know how many people are injured versus dead. Personnel and resources are initially mobilized in response to a shooting, regardless of the number of fatalities. Indiscriminate Selection of Victims. For this report's definition, a killer's relationship to his or her victims is important. Driven by a desire for revenge and/or power, some killers may target family members or intimate friends. In the incidents described as public mass shootings for this report, the gunmen cannot solely kill such individuals. This particularly rules out cases of domestic violence—instances only involving family members either inside or outside the home—from consideration as public mass shootings. Thus, for this report, the gunmen in public mass shootings somewhat indiscriminately select their victims. For example, a student assailant involved in a public mass shooting plans on killing particular teachers, while simultaneously staging a wider assault on his school. Violence Not a Means to an End. For this report, a public mass shooter's agenda certainly may stem from his specific personal experiences and psychological conditions. However, as implied in the above definition, the shooters who perpetrated the incidents counted in this report did not have broad socio-political objectives, such as using violence to advocate the fall of a regime. Thus, gunmen acting in the name of a terrorist organization or a clearly framed philosophy of hate typically were not considered public mass shooters. Also, shootings largely motivated by criminal profit were not counted. Based on the purpose undergirding the assailant's violence, the following examples do not fit the definition of public mass shooting used for this report. In December 2012, Dwayne Moore was convicted of home invasion, armed robbery , and four counts of first-degree murder in Massachusetts. He reportedly gunned down four victims, including a child, in a September 2010 drug-related incident in Boston, MA. A mass murder that has been widely reported as a hate-motivated incident occurred on the morning of August 5, 2012, when Wade Michael Page shot to death six people at the Sikh Temple of Wisconsin in Oak Creek—near Milwaukee, WI. According to the FBI, police responding to the scene returned fire, wounding Page. He then took his own life by shooting himself. U.S. Army Major Nidal Hasan was charged in a shooting at Fort Hood, TX, on November 5, 2009. The mass murder, which has been described as a terrorist incident , killed 13 and injured more than 40 others. To identify incidents of public mass shootings, CRS reviewed descriptions of mass shooting events found in scholarly journal articles, monographs, lists created by government entities and advocacy organizations, and news accounts. It is important to note that while every effort was made to be thorough in reviewing the sources used, the incidents identified by CRS should not be considered as constituting an exhaustive list of public mass shootings. Readers are also cautioned against tying this report's definition of public mass shootings directly to specific federal policy responses. In other words, the policy responses discussed below are not restricted to preventing or reacting to public mass shootings as defined in this report. For instance, many of the policy measures discussed herein respond to shooting events or threats that could include fewer than four deaths or shooters with specific ideologies and targets. The shooting definition offered in this report is meant to help illustrate the nature and breadth of a threat that lacks an agreed-upon conceptualization among experts, capturing some of the most extreme shooting cases over the last three decades. For many years, mass shootings have been of interest and concern to a variety of experts—including psychologists, sociologists, criminologists, public health experts, policy makers, and students of popular culture—who have written much on the topic. Journalists have tracked such killings for a long time as well. For example, a case involving gunman Howard B. Unruh in September 1949 received national attention. There were over 50 news articles in more than a dozen major newspapers in the United States in the month after the shooting occurred. In what was reported at the time as the largest mass murder in U.S. history, Unruh killed 13 people in a 20-minute-long incident in Camden, NJ. He shot people he knew as well as strangers. His victims included three children. All of this interest in such shootings has produced a wide variety of terms and concepts that address an assortment of issues. Categorizing types of murder—and mass shootings, more narrowly—can be tricky. In many cases, individual incidents involving assailants who kill one, two, or three people are described as single, double, or triple murder. However, when the number of victims rises or the case involves complicating circumstances such as the killer assailing individuals in different locations or a string of murders committed over a period of days, months, or years, efforts to define and understand murder can grow much more difficult.