Mass shootings may be done for personal or psychological reasons, such as by individuals who are deeply disgruntled, seeking notoriety, or are intensely angry at a perceived grievance; though they have also been used as a terrorist tactic, such as when members of an ethnic or religious minority are targeted.
[1] In its definition, a Congressional Research Service report from 2013 specifies four or more killings on indiscriminate victims, while excluding violence committed as a means to an end, such as robbery or terrorism.
[3] Mother Jones magazine defines mass shootings as indiscriminate rampages killing three or more individuals (not including the perpetrator), and excluding gang violence and armed robbery.
[7] Mass shootings (that occur in public locations) are usually committed by deeply disgruntled individuals who are seeking revenge as a motive, for failures in school, career, romance, or life in general.
"[39] Criminologist Gary Kleck criticized Lankford's findings, stating the study merely shows a proportional relationship but fails to prove that gun ownership causes mass shootings.
He speculated that Lankford had overlooked a significant number of mass shootings outside the U.S., which if accounted for would adjust the nation's share closer to 2.88 percent; slightly below the world average.
Because America had in those years approximately 4.5 percent of the world's population (according to Lott and Moody's calculations), this indicates that based on their data, the United States had more than six times its global share of public mass shooters who attacked alone (29.7/4.5 = 6.6).
[44] In a subsequent study, Lankford criticized Lott and Moody for including "attacks by terrorist organizations, genocidal militias, armed rebel groups, and paramilitary fighters" in their data and suggested they "misrepresent approximately 1,000 foreign cases from their own dataset" in other ways.
[47] Mass shootings (and firearm deaths in general) are exceedingly rare in China, Singapore, South Korea, Japan and the United Kingdom.
[65] According to a study by The Violence Project, 42 percent of all mass shooters experienced physical or sexual abuse, childhood trauma, parental suicide, or were victims of bullying.
However, Lankford and Cowan also emphasize that mental illness is not the sole cause of mass shootings and many other factors play an important role in perpetrators' decisions to attack.
[69] Mass shootings can be motivated by religious extremism, political ideologies (e.g., neo-Nazism, terrorism, white supremacism), racism, misogyny, homophobia, mental illness,[70][71] and revenge against bullying,[72] among other reasons.
[73] A study by Vanderbilt University researchers found that "fewer than five percent of the 120,000 gun-related killings in the United States between 2001 and 2010 were perpetrated by people diagnosed with mental illness.
"[74] John Roman of the Urban Institute argues that, while better access to mental health care, restricting high powered weapons, and creating a defensive infrastructure to combat terrorism are constructive, they do not address the greater issue, which is "we have a lot of really angry young men in our country and in the world.
"[76] He expanded on the concept in a 2015 New Republic essay on injustice collectors,[77] identifying several notorious killers as fitting the category, including Christopher Dorner, Elliot Rodger, Vester Flanagan, and Andrew Kehoe.
[78] In relation, criminologist James Alan Fox contends that mass murderers are "enabled by social isolation" and typically experience "years of disappointment and failure that produce a mix of profound hopelessness and deep-seated resentment.
"[79][80] Jillian Peterson, an assistant professor of criminology at Hamline University who is participating in the construction of a database on mass shooters, noted that two phenomena surface repeatedly in the statistics: hopelessness and a need for notoriety in life or in death.
[83] The Italian Marxist academic Franco Berardi argues that the hyper-individualism, social alienation and competitiveness fomented by neoliberal ideology and capitalism creates mass shooters by causing people to "malfunction.
Researchers studied the role the coverage plays in shaping attitudes toward persons with serious mental illness and public support for gun control policies.
[89] In 2015, a paper written by a physicist and statistician, Sherry Towers, along with four colleagues was published, which proved that there is indeed mass shooting contagion using mathematical modeling.
[90] However, in 2017, Towers said in an interview that she prefers self-regulation to censorship to address this issue, just like years ago major news outlets successfully prevent copycat suicide.
After the 2015 San Bernardino attack, the New York Daily News' front-page headline "God isn't fixing this" was accompanied by "images of tweets from leading Republicans who shared their 'thoughts' and 'prayers' for the shooting victims.
[106] According to British criminologist Peter Squires, who has studied gun violence in different countries, mass shootings may be more due to the "individualistic culture" in the U.S. than its firearm laws.
In recent years, the government has implemented various measures, including increasing security forces, deploying the military to high-risk areas, and tightening gun control laws.
On 22 July 2016, when a lone gunman named David Sonboly opened fire at a shopping mall in Munich, killing nine people and injuring 36 others.
Later, on 19 February 2020, a mentally unstable man named Tobias Rathjen opened fire at two shisha bars in the town of Hanau, killing nine people before turning the gun on himself.
Rathjen, who had a history of mental illness and far-right extremist views, left behind a manifesto in which he expressed his hatred for immigrants and called for the extermination of several ethnic groups.
In the Czech Republic, the first mass shooting in its independent history occurred on 8 March 2009, when a 42-year-old Macedonian national named Raif Kačar opened fire at the Sokol Restaurant in Petřvald, killing four.
On 10 December 2019, when 42-year-old Ctirad Vitásek, illegally armed with a CZ 75B, opened fire at the traumatology room of the Ostrava University Hospital [cs], killing seven and injuring two.
In France, On 13–14 November 2015, a series of religiously motivated mass shootings and suicide bombings occurred in Paris leading to the death of 130 people and 7 out of the 9 perpetrators.