The patterns and prevalence of mass murder in twentieth-century America

Even though previous research has not examined mass murder prior to 1965, scholars have asserted that the mid-1960s marked the onset of an unprecedented and ever-growing mass murder wave. Using news accounts and the FBI's Supplementary Homicide Reports (SHR) as sources of data, this study analyzes 909 mass killings that took place between 1900 and 1999. Although the mid-1960s marked the beginning of a mass murder wave, it was not unprecedented, because mass killings were nearly as common during the 1920s and 1930s. The results also show that familicides, the modal mass murder over the last several decades, were even more prevalent before the 1970s. Moreover, mass killers were older, more suicidal, and less likely to use guns in the first two-thirds of the 20th century. Although some have claimed that workplace massacres represent a new “strain” in mass murder, the findings suggest that the only new type of mass killing that emerged during the 20th century was the drug-related massacre.