Study Finds School Shootings, Mass Killings are 'Contagious'
Mass killings and school shootings spread "contagiously," a new study found, where one killing or shooting increases the chances that others will occur within about two weeks.
The study, published in the journal PLOS ONE, found evidence that school shootings and mass killings -- defined as four or more deaths -- spread "contagiously," and 20% to 30% of such killings appear to be the result of "infection." The contagion period lasts about 13 days, researchers found.