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Study: Mass shootings in the U.S. appear to be contagious

Researchers say contagion accounts for roughly 20 to 30 percent of all mass shootings.

By Brooks Hays
Accused movie theater shooter James Holmes (left) makes his first court appearance at the Arapahoe County Courthouse with his public defender Tamara Brady on July 23, 2012 in Centennial, Colorado. According to police, Holmes committed one of the worst mass shootings in American history, killing 12 people and injuring 58 when he opened fire on a movie theater showing the premier of "The Dark Knight Rises." File photo by RJ Sangosti/Pool/UPI
Accused movie theater shooter James Holmes (left) makes his first court appearance at the Arapahoe County Courthouse with his public defender Tamara Brady on July 23, 2012 in Centennial, Colorado. According to police, Holmes committed one of the worst mass shootings in American history, killing 12 people and injuring 58 when he opened fire on a movie theater showing the premier of "The Dark Knight Rises." File photo by RJ Sangosti/Pool/UPI | License Photo

TEMPE, Ariz., July 2 (UPI) -- Those who criticize the media's seemingly nonstop coverage of mass shootings may be onto something. New research suggests mass shootings begat more mass shootings.

Scientists at Arizona State University say mass violence statistics suggest the wicked inspiration for these deadly events -- whether at schools or in movie theaters -- may be contagious.

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"The hallmark of contagion is observing patterns of many events that are bunched in time, rather than occurring randomly in time," Sherry Towers, research professor at Arizona State's Simon A. Levin Mathematical, Computational and Modeling Sciences Center, explained in recent press release.

Towers is the lead author of a new study on the subject of mass shootings, published in the journal PLOS ONE.

Previous research has shown that contagion can be credited with inspiring suicides at schools. Statistics suggest news of a classmate's suicide can put the idea into the head of other vulnerable and depressed students.

In 2014, when Towers noticed a string of school violence happened within a two-week time frame, she wondered whether contagion might also explain mass shootings and similar attacks. The statistical evidence, she says, suggests yes.

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"It occurred to us that mass killings and school shootings that attract attention in the national news media can potentially do the same thing, but at a larger scale," Towers said. "While we can never determine which particular shootings were inspired by unconscious ideation, this analysis helps us understand aspects of the complex dynamics that can underlie these events."

In crunching the numbers, Towers and her colleagues determined contagion accounts for roughly 20 to 30 percent of all mass shootings, and that a contagion effect lasts for 13 days after an initial shooting.

The study also showed that mass shootings, involving the death of four or more people, occur an average of once every two weeks in the United States. School shootings occur once a month. Both, the researchers found, are more prevalent in states with higher levels of gun ownership.

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