Counting Mass Murder: Supplementing Current Mass Murder Tracking Systems Using NIBRS (A Short Report)

Due to inconsistent methods of counting incidents within research, government agencies, and private entities, the prevalence of mass murder in the United States remains uncertain. Mass murder is often defined by the number of homicide victims within a single incident, but variations in these thresholds can significantly alter our understanding of its prevalence. Recent research has found that from 2006 to 2020 there were a total of 448 mass killings, averaging approximately 30 a year (Fox & Levin, 2022). The current study utilizes the 3 + and 4 + murder counts respectively to uncover mass murder incidents in the National Incident-Based Reporting System (NIBRS). Using 2021 NIBRS data, this study identifies 166 (3 + homicide victims) mass murder incidents and 48 (4 + homicide victims). In total these findings suggest that the prevalence of mass murders, regardless of type (domestic, gang-related, school shooting, etc.) represents 1–3% of all homicide victims.