Self- and other-harm in mass shooters: A dual-harm analysis

Area of Science:

• Psychology
• Criminology
• Public Health

Background:

• Individuals with dual-harm histories (self- and other-harm) face elevated risks for negative outcomes.
• Understanding these risk factors is crucial for developing targeted interventions.

Purpose of the Study:

• To examine mass shooters through the lens of dual-harm.
• To compare risk factors across no-harm, single-harm, and dual-harm groups of mass shooters.

Main Methods:

• Analysis of 197 U.S. mass shooters in public incidents (≥4 fatalities) from August 1966 to January 2023.
• Categorization into no-harm, single-harm, or dual-harm based on histories of self-harm, aggression, and violent crime.
• Data sourced from The Violence Project Database.

Main Results:

• One-fifth (n=40) of mass shooters exhibited dual-harm.
• The dual-harm group showed the highest prevalence of most risk factors, including significantly more adverse childhood experiences.
• Dual-harm individuals had higher rates of sexual abuse, psychiatric hospitalization, mood disorders, and interest in past mass violence compared to no-harm and single-harm groups.

Conclusions:

• Mass violence is heterogeneous, with a high-risk dual-harm subset exhibiting complex needs.
• Identifying distinct harm-level groups aids in understanding the diverse experiences and behaviors within mass shooter populations.
• This trichotomy approach highlights a lower-risk no-harm group, underscoring the spectrum of risk.