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Is there a "typical profile" of the mass killer in the United States?

Mass killings, such as those on August 3 and 4 in El Paso (Texas) and Dayton (Ohio), have been in the news for a long time in the United States. Their recurrence leads to questioning their authors: do they have common characteristics related to their origins? What are their motivations? The studies show a lot of common traits, but they are not always the most obvious.

Read the latest information: Trump condemns white supremism without convincing his sincerity

1. These are more than 95% of men

It is the most obvious feature among mass murderers: it is almost always men. Among the main public shootings that the site of investigation Mother Jones since 1982, 111 of the 115 killers, or 96.5%, are male. The FBI, which lists active shooters since 2000, reported 277 shooters, including 265 men for 12 women, a 95.5% male precedence.

2. Whites are not overrepresented

After the El Paso shooting, Donald Trump has declared the "White supremacism". This ideology is at the origin of 17 killings having caused 105 deaths since 2012 in the United States. But does this mean that whites are more likely than others to commit mass murder? No. According to the analyzes of the last years, between 54% and 70% of these acts were perpetrated by whites. Yet, these are not overrepresented if these figures are compared to their proportion (73.9%) in the United States population. In other words, there are more white killers because there are more whites.

In an article published by Slate, columnist Daniel Engber notes that  € œThe claim on â € œWhite men are over-represented among mass murderersâ € serves a useful purpose in disqualifying another myth about mass killings according to which they are the work of dangerous immigrants (â € |). It's a laudable goal, but we should not have to learn other myths to achieve it. ".

Some trends emerge anyway. Thus, the killings targeting schools are mostly committed by young whites, according to an analysis of 111 cases by the New York Times. The data shows that they have accumulated more firearms than any other category: only 3% of the Haitian population now owns half the firearms of the country, according to the Injury Control Research Center of Harvard University. Many publications have also shown that moral and emotional attachment to guns was stronger among men (65%) and whites (78%).

3. Mental disorders are not decisive

Donald Trump said the killers of El Paso and Dayton were "Very, very mentally ill people". It is still too early to determine in either case, but studies of mass murderer profiles indicate that mental illnesses are not such a shared trait.

Even though having a psychiatric disorder increases on average the risk of being violent (three to four times more), the absolute risk remains very low and the vast majority of people will never be violent.

Research conducted by Michael Stone, a psychiatrist at Columbia University in 2015, shows that 52 of the 235 mass murderers he identified had mental illnesses, or 22%. A study published in 2001 in the Journal of the American Academy of Child and Adolescent Psychiatry Thirty-four adolescents also concluded that only 23% of the killers had documented psychiatric disorders.

Other factors are more profound, according to this work: 70% of the killers were described as solitary, 61% suffered from addictions to various substances and 43% had been victims of ds. • intimidation or harassment. The professor of psychiatry Jeffrey Swanson reminded however, in the media of investigation ProPublicain 2014, that "The risk factors of the perpetrators of mass killings are shared by a lot of people who will pose no risk".

According to this specialist, instead of focusing the attention and action of public authorities on psychiatric disorders, it would be more efficient to focus on  «behavioral indicators ». In a study of the risks of violence among people with mental disorders, researchers found three key factors: being a very young victim of violent acts, drug abuse and exposure to violence in its environment. Not to mention the personal history: "If someone has ever had violent or aggressive behavior, it's a better indicator of future violence than a psychiatric diagnosis.", recalls Jeffrey Swanson.

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4. A frequent desire for notoriety and revenge

Mass murderers often portray marginalized people, breaking with the group. Some of them have already suffered humiliations or intimidations to repetition in their youth, in the school or family. "There is almost always a personal grievance that will lead a person to mass murder.", said in 2015, Dr. J. Reid Meloy, a medical-legal psychologist, at New York Times.

The search for a local or national notorious break is often a primary or secondary motivation for mass murderers. This is the case for killings taking place in small communities where everyone knows each other. "The killer sees himself as a marginal and there are cultural scenarios that give him a model: the idea that if you go out and kill people, you will become an antihé © lèbre, who will do the â € œuneâ € of all newspapers  », according to Jeffrey Swanson. Christopher Harper-Mercer, who killed nine people in October 2015 on a university campus, wrote in a blog post before his action: "It seems like the more people you kill, the more you are in the spotlight. AT" Dylan Klebold, who murdered thirteen people at Columbine High School in 1999, said in a video before the slaughter that "Movie makers will fight to tell this story".

5. A proven contagion effect

Most killers study the modus operandi other killers before going into action themselves and regularly seeking to justify their actions, through the dissemination of a manifesto, which often refers to the actions of tu manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste manifeste other mass murderers, whose ideas will be largely mediated. "Many killings tend to happen in a group" At close frequencies, writes the Los Angeles Times. "They are socially contagious. AT"

In fact, mass killings obey, like all human behavior, the logic of social copying, that is to say that our behavior depends largely on those of others, present in our immediate environments (family, friends) but also in the more distant behaviors like those of other killers whose mediation of our societies considerably increases the scope.

In a July 2015 publication of Public Library of Scienceresearchers from the universities of Arizona and Illinois have shown that mass killings are indeed contagious and therefore prone to epidemics. This work, carried out with mathematical simulations on the basis of 232 mass killings, indicates that each event increases the probability of a future killing in the next thirteen days ( each killing resulted in 0.3 new killings on average). The authors also note that there is no "No significant evidence of contagion in mass killings involving fewer than four deaths", potentially implying that their higher frequency reduced the media echo and, therefore, their contagiousness.

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