Given the lack of one commonly accepted definition of a mass shooting, the number of mass shootings recorded depends greatly on the definition used.8 The Gun Violence Archive (GVA), an online database for gun violence incidents in the United States, defines a mass shooting as “four or more shot and/or killed in a single event [incident], at the same general time and location not including the shooter.”9 Using GVA’s definition, there were 418 mass shootings in the United States in 2019 — more than one every single day.

Mother Jones is another data source that collects information on mass shootings in the United States. They define mass shootings as “indiscriminate rampages in public places resulting in four or more victims killed by the attacker” and they “exclude shootings stemming from more conventionally motivated crimes such as armed robbery or gang violence.”10 Using this narrowed definition, Mother Jones found that there were only 10 mass shootings in 2019 and 118 from August 1982 through May 2020.

There are stark differences in these definitions and thus differences in the number of mass shootings recorded.10,11,12,13 Notably, the Mother Jones definition leaves out mass shootings in private places, many of which may be linked to domestic violence or community gun violence, thus leading to a drastically smaller number of mass shootings recorded per year. Without a universal definition of a mass shooting, and without accurate data, we will not know the true burden of mass shootings.11

No Uniform Definition

The lack of a uniform definition of a mass shooting creates inconsistencies when reporting on mass shootings and when seeking to understand the true burden these shootings have on our society. Inconsistent data makes it difficult to compare mass shootings in states, track changes over time, and fully understand the problem at the local and national level.

In addition to data reporting problems, there are problems with certain mass shootings being excluded, specifically neighborhood mass shootings and domestic violence-related mass shootings. When mass shootings are defined as events that occurred in one place, such as a school or a church, neighborhood mass shootings may be excluded. When definitions specify “public” violence, domestic violence mass shootings may be excluded.12,13

A 2019 study noted that when a broader definition of a mass shooting is used (four or more people killed or injured, including perpetrators), it captures more shootings of young Black men. Specifically, the study notes that “mass shootings largely affect the population at highest risk for firearm violence in cities: young Black men living in poor, under-resourced neighborhoods.”14,15 By using definitions that only include deaths, rather than both injuries and deaths, a large portion of gun violence in the United States is being discounted.

Mass casualty events, including those in communities and in the home, occur too often, and, as a result, have an enormous impact on the mental health, physical health, and overall wellbeing of Americans.16 However, in order to more accurately understand the different types of mass shootings and to develop effective policies to prevent such atrocities, there needs to be a uniform definition that does not include a restriction on location and counts both victims injured and killed.

“Although mass shootings are statistically rare, they still happen far too often. The thought of mass shooters attacking our public spaces — armed with deadly assault weapons — is many Americans’ worst fear. And this constant fear of mass shootings limits our ability to be truly free.”

- Bryan Barks, Director of Strategic Communications

Media Coverage of Mass Shootings

The media plays a significant role in how the American public discusses gun violence. The media focuses primarily on mass shootings and other high-profile homicides even though suicides make up three in every five gun deaths in the United States.17 In doing so, the media may lead the public to believe that mass shootings contribute to a large percentage of gun deaths in the United States, while in fact, firearm suicides comprise the majority of gun deaths. In fact, dying in a mass shooting is about as rare as being struck by lightning.18

Media coverage following a mass shooting also has implications for gun sales. For example, one study found that media coverage of mass shootings is associated with an increase in the number of firearms sold, as indicated by the number of background checks run.19

False Narratives

There are often two false narratives that emerge in the media after a mass shooting: 1) that mental illness causes gun violence, and 2) that if more people were armed, there would be fewer firearm-related deaths, and specifically, fewer mass shootings.20 If more guns made us safer, we would be the safest country in the world. Overwhelming evidence shows that firearm ownership and access is associated with increased homicides, suicides, unintentional firearm deaths, and injuries.21,22

The media often blames mental illness as the root cause of mass shootings. This is false — the majority of people with mental illness do not engage in violence against others, and most violence is caused by factors other than mental illness.23 Indeed, people with mental illness are more likely to be victims of violence than perpetrators of violence.24 The Educational Fund to Stop Gun Violence seeks to use data and research to highlight the evidence-based risk factors for violence and not further stigmatized individuals living with mental illness.

Progress After Mass Shootings

Mass shootings have often been the impetus for advancing gun violence prevention policies across the country.

On April 16, 2007, 32 people were murdered and 23 others were injured in a devastating mass shooting at Virginia Polytechnic Institute and State University. At the time and for years afterward, the massacre was the deadliest mass shooting in American history. The Virginia Tech shooting was a catalyst for change — in the years that followed, survivors and advocates on the ground in Virginia, including our own Lori Haas, worked tirelessly to change the gun laws in the commonwealth.

Thirteen years after the Virginia Tech shooting, Virginia Governor Ralph Northam signed a myriad of gun violence prevention bills into law, including universal background checks, extreme risk protection order legislation, and a child access prevention law.25

“I began lobbying for … changes to the commonwealth’s gun laws after my daughter was shot and injured and 32 others were murdered in their classrooms at Virginia Tech — 13 years ago next week. In those 13 years, Republican lawmakers have repeatedly rejected pleas for action on this public health epidemic. In that same time, regular Virginians became advocates and activists. They built community gun violence prevention groups. They protested monthly outside the National Rifle Association headquarters. They showed up in huge numbers for advocacy day to lobby their elected officials. When those officials ignored them, they voted them out. They elected governors who ran proudly on gun violence prevention platforms in 2013 and 2017. Then they flipped the House of Delegates and Senate in 2019. Now, with a GVP majority in the House and Senate and Governor Northam’s commitment, historic change is coming to Virginia.”

- Lori Haas, Senior Directory of Advocacy

Moms Demand Action for Gun Sense in America, the grassroots organization under Everytown for Gun Safety, was formed after the mass shooting at Sandy Hook Elementary School in Newtown, Connecticut in 2012. March for Our Lives, a youth-run gun violence prevention group, began organizing in all 50 states after the mass shooting in Parkland, Florida in 2018. Media coverage of these shootings galvanized individuals into action, resulting in the formation of new, highly organized groups.

After the shooting in Newtown, Connecticut, the Educational Fund to Stop Gun Violence convened the nation’s leading researchers, practitioners, and advocates in gun violence prevention, public health, law, and mental health. This group, called the Consortium for Risk-Based Firearm Policy (Consortium) met to discuss research evidence and identify areas of consensus regarding risk factors for future violence, specifically focusing on the relationship (or lack thereof) between mental illness and gun violence. This initial meeting resulted in a commitment to advance evidence-based gun violence prevention policy recommendations through the newly formed Consortium.

Policymakers have relied on the Consortium’s recommendations to craft legislation and executive action which continue to shape the policy landscape of the gun violence prevention movement. One of the most widely known policies developed by the Consortium is the Gun Violence Restraining Order or Extreme Risk Protection Order policy, detailed in their report entitled “Guns, Public Health and Mental Illness: An Evidence-Based Approach for State Policy.

Together, these groups create a stronger, more inclusive gun violence prevention network that, despite being formed after major mass shooting events, recognizes that gun violence is more than mass shootings.

No Notoriety

The Educational Fund to Stop Gun Violence firmly believes that we should not name the perpetrators of mass shootings. There is evidence to suggest a “contagion,” or imitation effect associated with mass shootings.26,27 In order to minimize this effect, the media — and others reporting on these incidents — should not glamorize shooters.

Survivors are often behind the “no notoriety” movement. Tom and Caren Teves created “No Notoriety” after their son was shot and killed in the July 2012 Aurora theater shooting. They implore the media “to eliminate the gratuitous use of the name and likeness of rampage mass killers, and shift the focus to the victims, heroes, and survivors.”28

As a result of this movement and many other calls-to-action from survivors and activists, the media has started to report on mass shootings more cautiously. Specifically, media reporting of mass shooting events now focuses more on the lives lost during the horrific event and less on the perpetrator.

Assault Weapons, Large Capacity Magazines, and Mass Shootings

Assault weapons and large capacity magazines often facilitate mass shootings and increase fatalities in such incidents. Evidence suggests banning these firearms, particularly large capacity magazines, could reduce mass shootings in the United States.29,30

Assault weapons

Assault weapons have been used in the deadliest mass shootings in the United States. The federal government banned assault weapons in 1994 but allowed the ban to expire after ten years in 2004. Seven of the ten deadliest mass shootings in American history occurred since 2004 when Congress let the federal assault weapons ban expire, and all seven of these shootings involved assault weapons that would have previously been banned by federal law.31 Only one of the 20 deadliest shootings in American history occurred during the decade when the ban was in place (1994-2004).32 While banning assault weapons will not stop all acts of gun violence, there is enormous potential to reduce the number of fatal mass shootings.

large capacity magazines

Large capacity magazines (magazines that hold more than ten rounds of ammunition, also known as high capacity magazines) contribute to more deaths and injuries in mass shooting incidents. Research suggests that banning large capacity magazines is one of the most effective ways to reduce fatal mass shootings.33 Large capacity magazine equipped weapons are so lethal in mass shootings because they enable rapid spray fire that allows shooters to wound a higher number of victims.

Large capacity magazines are used in half to two-thirds of public mass shootings and mass murders by firearm involving six or more fatalities.34 It is estimated the total number of victims wounded and killed in a mass shooting are two to three times higher when a large capacity magazine is used.35 States with state-level large capacity magazine restrictions report about 50% fewer mass murder incidents.36 Notably, researchers at Johns Hopkins School of Public Health concluded that “the capacity of the ammunition‐feeding device and the ability to quickly reload may be the most relevant feature of firearms that influence the incidence and outcomes of mass shootings.”37

To learn more, visit our page on assault weapons and large capacity magazines.

Risk Based Gun Laws and Mass Shootings

Reducing firearms access to people who may be at high risk of committing mass shootings is an important intervention. Risk based firearm laws, including extreme risk laws and domestic violence firearm restrictions, are designed to keep guns away from high-risk individuals and prevent tragedy.

Extreme Risk Laws

The majority of perpetrators of mass violence make concerning communications and/or elicit concern from others prior to carrying out their attacks.38,39 Waiting for an individual to act in a manner that would prompt a firearm prohibition sometimes means that the opportunity for intervention comes too late to prevent a tragedy. Extreme risk laws allow the people most likely to notice that an individual is at an elevated risk of violence — family or household members and law enforcement — to intervene before a tragedy occurs. Extreme risk laws create a legal process for temporarily prohibiting purchase and possession of firearms and removing firearms currently possessed from individuals who are at a higher risk of violence towards self or others but who are not otherwise prohibited from purchasing and possessing firearms because of a criminal conviction or other existing prohibitor. Preliminary evidence suggests that extreme risk laws can prevent and have prevented mass shootings. For example, researchers from U.C. Davis estimated that from 2016-2018, California’s extreme risk law was used in efforts to prevent 21 potential mass shootings.40

To learn more, visit our page on extreme risk laws.

Domestic Violence Prohibitions

Many mass shooters have histories of domestic violence, and domestic violence is considered a risk factor for perpetrating mass shootings.40 Nearly one-third of known mass shooters from 2014-2017 were suspected of domestic violence, many of whom had contact with the justice system for domestic violence.41 Further, more than half of mass shootings (when defined as four or more individuals fatally shot) involve the death of an intimate partner or family member.42 Implementing domestic violence firearm prohibitions can help reduce fatal mass shootings.

To learn more, visit our page on domestic violence and firearms.

Universal Background Checks and Licensing Laws

Universal background checks would close the loophole that currently allows prohibited purchasers to access guns by requiring background checks on all gun sales and transfers, including private and online sales. If properly implemented, universal background checks could prevent mass shootings, as they would reduce the likelihood a prohibited purchaser could access a firearm.43

Universal background checks have been found to be most effective when administered through a firearms licensing system. Licensing laws, also called permit-to-purchase laws, require individuals to obtain a license or permit before purchasing a firearm. These laws vary from state to state, but in addition to a background check, may require an in-person application, safety training, fingerprints, and a waiting period. Handgun purchaser licensing laws have been shown to be an effective policy and are associated with reducing fatal mass shootings.44

To learn more, visit our page on universal background checks.

The Ten Deadliest Mass Shootings

Five of the 10 deadliest mass shootings in American history occurred from 2016-2019.45 An assault weapon or large capacity magazine was used in every single one of these shootings. None of the 10 deadliest shootings occurred while the Federal Assault Weapons Ban was in place from 1994 to 2004.

SettingCityDateFatalitiesInjuriesWeapon Used
Las Vegas Strip, ConcertLas Vegas, Nevada10/1/20175854623 firearms, mostly rifles; including scopes, and two modified for "fully automatic" firing; two were mounted on tripods
NightclubOrlando, Florida6/12/20164953Semiautomatic rifle, semiautomatic handgun
Virginia Tech’s College CampusBlacksburg, Virginia4/16/20073223Two semiautomatic handguns
Sandy Hook Elementary SchoolNewtown, Connecticut12/14/2012272Two semiautomatic handguns, one rifle (assault), one shotgun (assault)
Texas First Baptist ChurchSutherland Springs, Texas11/5/20172620Semiautomatic rifle
Luby's CafeteriaKilleen, Texas10/16/19912420Two semiautomatic handguns
El Paso WalmartEl Paso, Texas8/3/20192226Semiautomatic rifle
San Ysidro McDonald'sSan Ysidro, California7/18/19842219One semiautomatic handgun, one rifle (assault), one shotgun
Marjory Stoneman Douglas High SchoolParkland, Florida2/14/20181717Semiautomatic rifle
United States Postal ServiceEdmond, Oklahoma8/20/1986156Three semiautomatic handguns

Adapted from: Follman M, Aronsen G, & Pan D. (2020). US Mass Shootings, 1982-2020: Data From Mother Jones’ Investigation. Mother Jones.

Aftermath of Mass Shootings

Mass shootings have wide-reaching impacts and affect more than those shot or killed. Though rare, mass shootings impact the mental wellbeing of society.46

Exposure to gun violence is widespread, and the trauma it inflicts impacts health, well-being, productivity, and happiness. Gun violence exposure changes the chemistry in the brain and can have lasting impacts on health, well-being, and development if left untreated.48

A survey conducted after the August 2019 mass shootings in Dayton, Ohio and El Paso, Texas found that nearly 80% of Americans experience stress following a mass shooting.49 In addition, the survey found that one-third of American adults say they fear going to certain public places due to mass shootings.50 Preventing mass shootings is necessary to prevent not only death and injury from gun violence, but to prevent the long-lasting trauma and impact that people feel after being exposed to such violence.

Gun violence takes both a human and economic toll, and we have a moral obligation to address it. The total estimated economic cost of gun violence in the U.S. is $229 billion each year.51 Each gun death, on average, costs society over $6 million. Each nonfatal gun injury, on average, costs society an estimated $583,000. The cost of inaction is far more costly than gun violence prevention.

To learn more, visit our page on nonfatal gun violence.


Enact and implement policies that reduce easy access to firearms by people at elevated risk of interpersonal violence and ban assault weapons and large capacity magazines that increase lethality in mass shootings.

Americans have become far too familiar with mass shootings, but it doesn’t have to be this way. Laws that reduce easy access to firearms for people at risk of violence and ban assault weapons and large capacity magazines are associated with reductions in mass shootings and associated fatalities. We recommend the following policies:

  • Banning assault weapons and large capacity magazines: Assault weapons and large capacity magazines increase fatalities in mass shootings and don’t belong in our communities. Research has found that banning large capacity magazines is effective at reducing mass shootings. Congress should reinstate the federal ban on assault weapons and large capacity magazines. In the absence of federal action, states should continue to enact assault weapons and large capacity magazine bans. See Assault Weapons and Large Capacity Magazines for more information.
  • Extreme risk laws: Extreme risk laws empower law enforcement and the people closest to an individual at elevated risk of harm to self or others to intervene to help prevent gun tragedies before they occur. These state laws allow law enforcement, and in some states family and household members, among others, to petition a judge to temporarily limit an individual’s access to firearms if they are at elevated risk of violence. Evidence suggests extreme risk laws may be used to help prevent mass shootings. Every state should have its own extreme risk law and continuously monitor and evaluate the law to ensure equitable implementation and ongoing effectiveness. See Extreme Risk Laws for more information.
  • Universal background checks with licensing: Universal background checks require a background check on all firearm sales and transfers. Without universal background checks, it is far too easy for prohibited purchasers to acquire firearms. Background checks should be required on every gun sale and transfer in the United States, including private and online sales. See Universal Background Checks for more information. Universal background checks are found to be most effective when administered through a firearms licensing system. Licensing laws, also called permit-to-purchase laws, require individuals to obtain a license or permit before purchasing a firearm. These laws vary from state to state, but in addition to a background check, may require an in-person application, safety training, fingerprints, and a waiting period. Research has found that these laws are effective at reducing mass shootings. States should enact licensing laws and continuously monitor and evaluate the law to ensure equitable implementation.
  • Domestic violence firearm prohibitions: Many mass shootings are related to domestic violence. Laws that reduce abusers’ access to firearms are associated with reductions in intimate partner homicide and may also prevent mass shootings. Such laws should be enacted at the state and federal levels. See Domestic Violence and Firearms for more information.
  • Establish a federal definition for a mass shooting: There is no legal definition of “mass shooting” under federal law and current variations in the definitions used can result in undercounts of incidents and victims. The lack of a uniform definition hinders data collection and analysis, which is the foundation of the public health approach to preventing gun violence. The federal government should establish the definition of a mass shooting as four or more injured or killed, excluding the perpetrator, regardless of place or gang and/or drug involvement.
  • Data collection and reporting: There is no formal collection and reporting of data related to mass shootings, including fatalities and the role of firearms. Inconsistent — or even nonexistent — data makes it difficult to compare mass shootings in states, track changes over time, and fully understand the problem at either the state or national level. Having accurate data is fundamental to effective prevention. Congress should direct the Bureau of Justice Statistics, or similar agency, to formally track mass shootings and include data related to the number of victims killed and wounded, the role of firearms, and setting – ensuring mass violence events that occur in public and private settings are captured – among others.


Educational Materials

Read More


Additional Resources

Last updated July 2020