But after 10 die in second mass-casualty school shooting of 2018, experts say tragedies not necessarily becoming more common

On Friday, 10 people were killed in a school shooting in Santa Fe, Texas. Just two days earlier, a former student opened fire at a high school in Dixon, Illinois. The officer who quickly stopped the shooter was hailed as a hero.

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Researchers who have studied American mass shootings have found evidence of a “contagion effect”. In the two weeks after a mass shooting or school shooting, one 2015 study found, there is an elevated likelihood that another mass shooting or school shooting will take place.

About 20% to 30% of the incidents studied “appeared to be inspired by contagion”, said the lead author of the paper, Sherry Towers, a professor at Arizona State University who specializes in mathematical and computational modeling.

Some of the most horrific shootings appear to inspire new shootings not only for weeks but for decades. A common thread in the histories of many mass shooters is an obsession with previous shootings, particularly the 1999 shooting and bomb attack at Columbine high school in Colorado.

“Some of these incidents have a longer contagion than others do,” Towers said.



Elementary and high school students have grown up practicing “active shooter drills” along with fire drills, preparing for how they should respond if a gunman attacks.

“It’s been happening everywhere; I’ve always kind of felt like eventually it was going to happen here too,” the Santa Fe student Paige Curry told the media after the shooting on Friday. Her response went viral.

Towers, however, was cautious about the idea that school shootings were becoming common.

“The idea that we’re spiraling out of control in school shootings is perhaps not supported by the data,” she said. “That being said, the US per capita has a far higher rate of school shootings compared to any other developed country.”

In the first six months of 2018, there have been two mass shootings – shootings with four or more people killed – at American high schools, Towers said. There were only two mass shootings at K-12 schools in the decade prior.

It’s not that it’s an infectious disease. It’s something that if someone is in a particular mindset, they can emulate Peter Sheridan Dodds, University of Vermont

“Yes, that is an unusually high number to have in a relatively short period of time,” she said. “Whether or not this is the beginning of a trend in increasing rates remains to be seen.”

The “contagion effect” in school shootings does not mean that the risk of becoming a school shooter is contagious in the same way measles or ebola are, said Peter Sheridan Dodds, a professor of mathematics and statistics at the University of Vermont and one of the authors of a 2017 study that found an association between the level of social media chatter about school shootings and the probability of new attacks.

“It’s not that it’s an infectious disease. It’s something that if someone is in a particular mindset, they can emulate,” he said.

Dodds thinks of school shootings as a pathway previous attackers developed – a pathway that very few people will ever be tempted to take but which has become extremely well documented in the media and in American culture. Though most people will never be interested in following that path, “it’s not hard to figure out how to emulate it,” he said.

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Some law enforcement officials and parents of Americans killed in mass shootings have urged news organizations to change the way they respond, to give the perpetrators less notoriety, and to avoid coverage that glamorizes perpetrators who seem to be seeking fame.

But Towers said that while it was important to acknowledge the contagion effect in mass shootings, to focus only on media coverage and the way some shootings appear inspired by previous attacks was to miss other crucial risk factors.

“One of the things that commonly gets pushed is that it’s all about the contagion,” she said. “What’s missed often is the other conclusion of that paper, which found that the availability of firearms is clearly playing a role, a significant role.

“States that had a lower prevalence of gun ownership had a lower per capita rate of mass shootings, so it’s not just a contagion effect.

“Just focusing on the media component of contagion is missing the entire story. And focusing on one aspect of it is not going to yield a solution.”