Included with the current update to the Profiles of Individual Radicalization in the United States (PIRUS) data are a suite of variables that allow users to investigate extremist offenders who plotted to commit, or committed, mass casualty attacks in the United States from 1990-2021. A mass casualty plot is defined as an event in which the perpetrator(s) intended to kill or injure four or more victims. Unlike other data resources on mass casualty events, PIRUS allows users to investigate successful mass casualty attacks as well as unsuccessful plots where the perpetrators clearly intended to kill or injure four or more people but failed. The inclusion of failed and foiled mass casualty plots in PIRUS gives users a more accurate estimate of how often extremists plan to cause significant harm. It also allows users to compare ideological groups and offenders on measures of plot success. This research brief provides an overview of the mass casualty crimes in PIRUS, including their frequency, links to ideological and sub-ideological groups, and a comparison of their perpetrators.
Jensen, Michael, Sheehan Kane, and Elena Akers. 2023. "Profiles of Individual Radicalization in the United States (PIRUS): Mass Casualty Extremist Offenders." College Park, MD: START (March). https://www.start.umd.edu/sites/default/files/publications/local_attachments/PIRUS-Mass%20Casualty%20Extremist%20Offenders_0.pdf