By Jillian Peterson; Gina Erickson; Kyle Knapp; and James Densley

Understanding the motivation of a mass shooter’s intent to do harm can help practitioners and policy makers develop more effective intervention strategies. OBJECTIVE To examine the prevalence of communication of intent to do harm, known as leakage, in a sample of 170 mass public shooters from 1966 to 2019; the characteristics of perpetrators who do and do not leak their plans; and whether leakage is a form of fame-seeking behavior or a cry for help among individuals who are in crisis or suicidal. DESIGN, SETTING, AND PARTICIPANTS This cross-sectional study included perpetrators who killed 4 or more people in a public space from 1996 to 2019 and were included in a comprehensive database of US mass shootings. That database was built from August 2017 to December 2019, and analysis took place from January to May 2021. MAIN OUTCOMES AND MEASURES Leakage was identified and coded using publicly available records. Any communication to a third party of an intent to do harm prior to the shooting was coded as leakage. Logistic regression models were used to examine the risk factors associated with leakage. Models estimating leakage were examined to assess the 2 hypothesized pathways to leakage (the cry-for-help model and the fame-seeking model). RESULTS The 170 participants in this sample included 166 (97.7%) male perpetrators and 3 (2.3%) female perpetrators, with a mean (SD) age of 34 (12) years. Overall, 161 participants had known race and ethnicity: 11 (6.8%) Asian individuals, 35 (21.7%) Black individuals, 14 (8.7%) Latinx individuals, 7 (4.4%) Middle Eastern individuals, 3 (1.9%) Native American individuals, 89 (55.3%) White individuals, and 2 (1.2%) individuals with other race and ethnicity. Overall, 79 mass shooters (46.5%) leaked their plans. Of perpetrators who leaked their plans, 35 (44.3%) leaked specific plans about a mass shooting, and 44 (55.1%) leaked nonspecific plans about generalized violence. The study findings indicate that leakage was associated with receiving counseling (odds ratio, 7.0; 95% CI, 2.0-24.8) and suicidality (odds ratio, 3.7; 95% CI, 1.0-13.6), suggesting that leakage may best be characterized as a cry for help from perpetrators prior to their act.  

JAMA Netw Open. 2021;4(11):e2133073. doi:10.1001/jamanetworkopen.2021.33073

By Jens F. Binder and Jonathan Kenyon

This work is concerned with the extent and magnitude of threat related to online radicalization in the context of terrorist acts and related offending. Online influences have been depicted as major drivers for the propagation and adoption of extremist ideologies, which often contain an element of collective grievance, and subsequent acts of violence. This is most pronounced in the discussion of so-called lone actor terrorism, but extends to all forms of extremist offending, and beyond. The present work situates online radicalization leading to terrorist acts within the wider context of grievance-based beliefs and attitudes. Further, it addresses current positions and debates surrounding the relevance and mechanisms of online radicalization in terrorist offending. Recent evidence from quantitative studies is reviewed to estimate prevalence of online radicalization and the level of threat that results from it. This is followed by a discussion of plausible, but opposing, interpretations of the estimates presented. While online radicalization does occur, with and without reference to offline processes, the resulting threat is not overly high. This assessment, however, refers to the present only and is unlikely to hold for the future, given the general growth and acceleration of online activity among terrorist actors

United Kingdom: Forensic and Legal Psychology, 2022, 10p.

By Nowrasteh, Alex

From the document: "Terrorism is a hazard to human life and material prosperity that should be addressed in a sensible manner whereby the benefits of actions taken to contain it outweigh the costs. A total of 219 foreign-born terrorists were responsible for 3,046 murders on U.S. soil from 1975 through the end of 2022. The chance of a person perishing in a terrorist attack committed by a foreigner on U.S. soil over the 48-year period studied here is 1 in 4.3 million per year. The hazard posed by foreigners who entered on different visa categories varies considerably. For instance, the annual chance of an American being murdered in a terrorist attack by a refugee is about 1 in 3.3 billion, while the annual chance of being murdered in an attack committed by an illegal immigrant is zero. Looking at this spectrum of risk, any government response to terrorism must consider the wide range of hazards posed by foreign-born terrorists who entered under various visa categories. There were 219 foreign-born terrorists who planned, attempted, or carried out attacks on U.S. soil from 1975 through 2022. Of those, 67 percent were Islamists, 16 percent were foreign nationalists, 6 percent were right-wing extremists, 5 percent were non-Islamic religious terrorists, 4 percent were left-wing extremists, and the rest were separatists, adherents of other or unknown ideologies, or targeted worshippers of specific religions. The federal government has an important role in screening all foreigners who enter the United States and excluding those who pose a threat to the national security, safety, or health of Americans, as foreign-born terrorists explicitly do. This focused terrorism risk analysis can aid in the efficient allocation of scarce government-security resources to best counter the small threat of foreign-born terrorists."

CATO Policy Analysis No. 958. 2023.

By Lynn M. Wright

The domestic terrorist threat in the United States is active and complex, with ongoing threats from violent left- and right-wing extremist groups, and radicalization and recruitment efforts by international terrorist groups. In response, domestic intelligence agencies, at all levels of government, have instituted reforms and improvements since 9/11, but there are still gaps in information-sharing and community engagement. For example, a review of the Boston Marathon bombings uncovered that important risk-based information was not shared with local law enforcement. Concerning domestic terrorism, the United States may, once again, be failing to “connect the dots.” This thesis synthesizes existing studies, reports, and expert testimony concerning domestic terrorism and the roles of domestic intelligence agencies, law enforcement, and the public, and proposes the development and implementation of a formal, national counterterrorism (CT) doctrine. The CT doctrine, in conjunction with a counter radicalization strategy, should focus on bottom-up intelligence/information-sharing, training to strengthen and focus intelligence collection efforts, and culturally sensitive and engaging messaging on social media and the Internet to counter extremist propaganda.

Monterey, CA: Naval Postgraduate School. 2014. 116p.