Gilroy, El Paso, Dayton.
a mathematical model found that shootings that resulted in at least four deaths launched a period of contagion, marked by a heightened likelihood of more bloodshed, lasting an average of 13 days.
And this study says media coverage is the cause of the contagion
Our findings consistently suggest that media coverage systematically causes future mass shootings. … A range of robustness checks support these conclusions. Using our benchmark estimation, a simple back-of-the-envelope calculation suggests that 58 percent of all mass shootings between January 1, 2013 and June 23, 2016 are explainable by news coverage. In terms of timeframes, news coverage seems to systematically raise the number of mass shootings in the following four to ten days and the effect reverts back to statistical insignificance after approximately 12 days.
Some ideas on how to reduce the media contagion effect in this, including giving no notoriety to to the shooters (don’t name them, don’t publish their photos):
Mass shootings may not actually be more frequent than they have been over the last 50 years. Our perception has changed to indicate it’s an epidemic, thanks to the media, but that’s not what the trends of actual data show.
While different choices about how to define a mass shooting and the period over which to calculate mass shooting trends have resulted in disagreement about whether the frequency of mass shootings has risen, there is clear evidence that the media’s use of the term mass shooting has increased significantly over recent decades (Roeder, 2016). Unfortunately, the ambiguity in how mass shootings are defined and counted may result in increased media coverage influencing public perception without better informing our understanding of the prevalence of mass shootings or their determinants, trends, social costs, or policy implications.
From here, an article worth reading: https://www.rand.org/research/gun-policy/analysis/essays/mass-shootings.html