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Mass Murder Trending

The contribution of contagion, cultural scripts, and cyberspace to mass killings

The Slaughterhouse 2015, with apologies to Kurt Vonnegut, continues. Although the figure of more than one mass murder a day in the U.S. during this past year is misleading—but was still promulgated by CNN without any clarification following the killings in Colorado Springs and San Bernardino—the fact that mass murder of civilians, excluding gang violence and domestic violence, is increasing cannot be disputed. There are, moreover, three aspects to this phenomenon which appear to provide a strong undercurrent to this inexplicable loss of life: contagion, cultural script and cyberspace.


Ever since a young man in the throes of chronic catathymia committed suicide in the Sorrows of Young Werther, a novel by Goethe published in 18th century Germany—and subsequent young people imitated his behavior—threat assessors from all disciplines have recognized the contagion effect. Although most of the research until recently has focused upon suicide, a recent study has empirically demonstrated its presence among mass murderers. Towers and her colleagues[1] at Arizona State University applied a contagion statistical model to three data sets: 232 mass murder events (4 victims killed) between 2006-2013, 188 school shootings between 1997-2013, and 376 mass murder incidents between 2005-2013 (4 victims killed)—and verified the independence of their data sets. They found by statistically applying a self-excitation contagion model to the data that there was a significant effect for the first two samples; but they also found a lack of geospatial influence, implicating widespread media dispersion of the incident as the primary awareness vector. The contagion effect, or temporary increase in the probability of another event, lasted on average for 13 days before there was a return to baseline. They also found that the frequency of all three data sets was associated with state prevalence of firearm ownership, but not mental illness.

Cultural Script

Intermittent contagion effects over time may become embedded in the culture as a script—a sociological term for an interpretive background within which people frame their interactions with others—which, in aggregated individual cases, is psychologically defined by the colloquial phrase “copycat effect.” At a deeper level, a copycat effect is an unconscious identification with, and conscious imitation of another person’s appearance or behavior[2]. One contemporary example is the “Columbine Effect” following the mass murder in Colorado in 1999. Mother Jones magazine[3] documented at least 72 mass murder plots and attacks inspired by Columbine, 21 of which were carried out and killed 89 people. Outside the U.S., this phenomenon is most evident in Germany; in a study in which we analyzed nine school shootings between 1999-2010, three of them were directly inspired by Columbine.[4] Although cultural scripting commands a macro look at one’s society, at an individual level where most of us live, it means we need to be aware of identifications with previous perpetrators that are seen in a person about whom we are concerned: a desire to be a pseudo-commando, fascination with weapons and other military paraphernalia, wanting to imitate previous attackers or assassins, or seeing oneself as an agent or soldier to advance a particular belief system or cause[5]. In case after case, we have also seen examples of theme consistency or scene specificity, the deliberate action recreation of a previous event, in post-offense mass murder reconstructions which hint at the identifications that lie beneath.[6] Mass murderers typically want to imitate those who have killed before them, and also enviously want to diminish their importance by attaining a greater degree of infamy, often through a higher body count or innovation in tactics, including creative means of broadcasting their criminal acts.


Two studies have independently demonstrated that targeted violence of civilians and mass murder are on the increase in the U.S. The first, conducted by Cohen and her colleagues[7] at the Harvard University School of Public Health, found that between 1982 and 2011, there was a mass murder—four or more dead victims in a public place, unrelated to one another--on average every 200 days; between 2011-2014, the average time between mass murders in the U.S. decreased to 64 days. The FBI active shooter study[8], published in 2014, found that when closely related cases—intentionally attempting to kill people in a public place—were compared between 2000-2006 and 2007-2013, the frequency increased 150%. These two studies’ findings, despite variations in definition, highly correlated with one another.

What is the cause of this increase? Although there are no definitive findings, but much speculation, a large contributing factor toward this increase appears to be cyberspace, especially the advent of widely used social media. The contribution comes in two forms:

Legacy tokens—We have known for many years that some people who commit mass murder want to be remembered for their infamous acts. The internet has made this remarkably easy. The cases are too numerous to detail, but there is clearly a trend as the ease with which one can be remembered in cyberspace has increased. The Columbine killers made videos to be found after their rampage in 1999. Seung Cho, the Virginia Tech mass murderer in 2007, tinkered with a DVD on which he placed a number of still photos and video edits of himself, and eventually mailed it to NBC News in between the time he killed his first two victims and a few hours later when he massacred dozens of people; George Sodini blogged about his intent to commit a mass murder for months before he did so in 2009, and killed three women while they were exercising at an LA Fitness studio in Pennsylvania; Anders Breivik, the Norwegian mass murderer, uploaded a 1500 page manifesto and sent it out to his mailing list in the hours before he eventually killed 77 in July, 2011; Jared Loughner (2011) and Eliot Rodger (2014) uploaded videos to YouTube documenting both their paranoia and narcissism in the months before they killed multiple victims in Tucson and Santa Barbara. And Vester Flanagan videotaped with a GoPro camera during his double homicide in Roanoke, Virginia, and then uploaded it to his Twitter and Facebook accounts before he committed suicide several hours later in August, 2015. Notice the trend: as technology accelerates and platforms proliferate, the ease increases with which one can use cyberspace to establish a “legacy token,” a phrase coined by Supervisory Special Agent Andre Simons of the FBI. What is next? The fear among threat assessors is the use of an App to stream a live broadcast of a mass murder by a criminal. Notice also, however, that this trend-line from DVD, to DVD sent through the mail, to blogging, to uploading a document, to uploading videos beforehand, to uploading a video of the killing, becomes increasingly more efficient as the technology does, but does not involve virtual engagement with others. There is also an interactive dark side.

Cajoling and recruitment—Nadir Soofi and Elton Simpson drove from Phoenix to Texas on May 3, 2015, with the intent of attacking a Mohammed cartoon convention with assault rifles. They were instantly killed by a police officer at the first security perimeter as they attempted to leave their car. Here’s a twitter feed just prior to their deaths:

ISIS Cajoler #1: The brothers from the Charlie Hebdo attack did their part. It’s time for brothers in the U.S. to do their part.

ISIS Cajoler #2: If there is no check on the freedom of your speech, then let your hearts be open to the freedom of our actions.

ISIS Cajoler #2: Kill those that insult the prophet.

Simpson: The bro with me and myself have given bayat (oath of allegiance) to Abu Bakr al-Baghdadi. May Allah accept us as mujahedeen.

ISIS Cajoler #2: Allahu Akbar!!!! Two of our brothers just opened fire at the Prophet Mohammad (s.a.w.) art exhibition in Texas! #TexasAttack

This was an ideologically motivated act of terrorism. A non-ideological mass murder illustrating the same cajoling occurred in Oregon five months later. Christopher Harper-Mercer killed a professor and 8 students at Umpqua Community College on October 1, 2015. The night before he posted to an anonymized listserv, and here are some of the responses from many individuals:

Harper-Mercer: Some of you guys are alright. Don’t go to school tomorrow if you are in the northwest. Happening thread will be posted tomorrow morning. So long space robots.

Response: Seattle or Portland? I’ll be watching the news.

Harper-Mercer: Will post again in am, 10 min countdown. Won’t say more too much to prepare.

Response: Nobody cares, you’re pathetic, and this is why no one likes you.

Response: DO IT. Be American. Get shot.

Response: I suggest you enter a classroom and tell people you will take them hostages. Make everyone get in one corner and then open fire.

Response: Make sure there is no one that can disarm you… I suggest you carry a knife on your belt as last resort.

Response: You might want to target a girls’ school, which is safer because there are no beta males throwing themselves for their rescue.

Response: Do not use a shotgun. I would suggest an assault rifle and a pistol or 2x pistols. Possibly the type of pistols that have 15+ ammo.

Response: Why don’t you just talk to a girl instead you beta fuck.

Response: It takes a great man to do great things. Become Legendary.

Response: You’re only shooting college age students, correct? I have grandparents that live up there.

Response: I can’t tell if you’re an edgy fag with aspergers or just shitposting havin’ a laff.

Oct. 1, 2014, 1434:




Harper-Mercer also expressed his admiration for Vester Flanagan, the man who killed two TV professionals while filming his murders in Roanoke, Virginia, on August 26, 2015, slightly more than a month earlier—an example of the copycat effect.

Contagion, cultural scripts, and cyberspace are some of the terrestrial and virtual social realities which are contributing to the increasing mass murder incidence in the United States. Threat assessment and threat management means we defend against these phenomena through our own situational awareness of behaviors of concern, whether in the real world or online. If we see something, we say something.


[1] Towers S, Gomez-Lievano A, Khan M, Mubayi A, Castillo-Chavez C. (2015). Contagion in mass killings and school shootings. PLoS ONE 10 (7). DOI:10.1371/journal.pone.0117259

[2] Meloy JR, Mohandie K, Knoll J, Hoffmann J (2015). The concept of identification in threat assessment. Behavioral Sciences and the Law DOI: 10.1002/bsl.2166

[3] Follman M. (2015). Trigger warnings: inside the race to identify and stop the next mass shooter. Mother Jones, November-December, pp. 23-29.

[4] Meloy JR, Hoffmann J, Roshdi K, Guldimann A. (2014). Some warning behaviors discriminate between school shooters and other students of concern. J Threat Assessment and Management 1:203-211.

[5] See footnote 2.

[6] Meloy JR, Mohandie K. (2001). Investigating the role of screen violence in specific homicide cases. J Forensic Sciences 46:1113-1118.

[7] Cohen A, Azrael D, Miller M (2014). Rate of mass shootings have tripled since 2011. Mother Jones, Oct. 15.…

[8] Blair J, Schweit K. (2014). A Study of Active Shooter Incidents in the United States between 2000 and 2013. Texas State University and Federal Bureau of Investigation, U.S. Dept of Justice, Washington, D.C.

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