What Effect does Ideological Extremism have on Mass Shootings? An Assessment of Motivational Inconsistencies, Risk Profiles, and Attack Behaviors

Much like other violent extremists, some mass shooters embrace inconsistent, mixed, or customized beliefs and attack for a combination of personal and ideological reasons. This makes it difficult to understand what effects ideology has on their behavior. To obtain empirical answers, we studied (1) the frequency of extreme ideological interests and motives among public mass shooters, (2) differences between perpetrators with and without extreme ideological interests, and (3) the degree of consistency between their ideologies and attack outcomes. Findings suggest that from 1966–2023, approximately one-quarter of public mass shooters in the United States had extreme ideological interests and roughly 70 percent of them were partially motivated by those extreme beliefs. Mass shooters with and without extremist interests showed similar rates of childhood trauma, mental health problems, suicidality, crisis, substance abuse, and criminal records, but ideological shooters were more likely to create legacy tokens, use semi-automatic or automatic rifles, kill strangers and non-white victims, and be copycats or role models. It appears extremism was sometimes a correlate and sometimes a cause of their behavior, with a clear effect on shaping some attacks. Nevertheless, inconsistencies were common, and many attackers did not target locations or victims that fit their ideological enemies.