Yesterday we noted that mass shootings appear driven by “contagion,” a word researchers began using several years ago to describe the phenomenon. Pay attention to the second part of this CBS News report on the arrest of a 37-year-old Marriott Hotel cook in Southern California, who had acquired quite an arsenal to fulfill his threat of a mass shooting at work. Rodolfo Montoya is the twenty-ninth person arrested for suspected threats of mass shootings since El Paso and Dayton:

The threat from Montoya certainly looked serious and acute. One of his co-workers took it seriously enough to call police, but his co-workers had considered him somewhat strange and threatening for a while, too:

A disgruntled Marriott employee who had an enormous arsenal of weapons stashed at his home was arrested after telling a colleague he planned to carry out a mass shooting at his workplace, authorities have said.

Rodolfo Montoya, of Huntington Beach, California, was allegedly plotting to murder his co-workers and Marriott hotel guests with his cache of high-powered firearms – including two assault rifles, a pump-action shotgun and several pistols – following an undisclosed dispute with his HR department.

But his plan was foiled when the 37-year-old cook let slip his deadly intentions to a colleague who informed their manager. The manager then called the Long Beach Police Department who raided Montoya’s home and seized the stockpile of weapons. …

‘Multiple firearms, hundreds of rounds of ammunition and tactical gear were seized, including high-capacity magazines and an assault rifle, which are illegal to possess in California,’ Long Beach Police officials said in a statement late Wednesday.

Montoya was charged with manufacturing and distributing assault weapons, possession of an assault weapon and making a criminal threat. He is currently being held on $500,000 bail at the Long Beach City Jail.

California, it should be noted, has some of the nation’s toughest gun-control laws.

Beyond that, how did we get from two mass shootings to twenty-nine potential others in just two weeks? Again, let’s return to this explanation from The Atlantic two years ago, in which Arizona State University researchers postulated a connection between mass shootings and media coverage of previous incidents, after establishing that these incidents appear to cluster together, again emphasis mine:

But according to a 2015 paper out of Arizona State University, “Contagion in Mass Killings and School Shootings,” there are some data that mass shootings often occur in bunches, which indicates that they “infect” new potential murderers, not unlike a disease. “We find significant evidence that mass killings involving firearms are incented by similar events in the immediate past,” the authors wrote. Suicide and terrorism, too, have been found to be likewise contagious. (Interestingly, the authors found “no significant association” between the rate of school and mass shootings and the state’s prevalence of mental illness.)

Diseases spread among individuals, but the contagion of mass shootings seems to spread through broadcast media. In an interview with The Atlantic in 2015, Sherry Towers, the ASU paper’s lead author, hypothesized that television, radio, and other media exposure might be the vectors through which one mass shooting infects the next perpetrator. Like a commercial, each event’s extraordinary coverage offers accidental advertising for depravity. One reason why mass-media coverage of shootings might inspire more shootings is that public glorification inspires some mass murderers. Eric Harris, the central planner of the Columbine murders, wrote Ich bin Gott—German for “I am God”—in his school planner.

Excessive media coverage doesn’t make people crazy. However, the obsessive nature of coverage of mass shootings — and political exploitation of them — incentivized already-borderline people to tip over and use mass shootings as a way to express their malice and frustration. It’s very difficult to believe that there were twenty-nine acute threats before El Paso and Dayton and the obsessive coverage that those shootings produced — although it’s rather easy to believe that Montoya in particular probably was a threat well before then.

How long will we go before the media — especially the broadcast media — begin considering how to contain the contagion?