Pulse nightclub. Mandalay Bay. Fort Hood. Emmanuel AME Church. Each time a terrorist attack occurs, the media interview those who knew the attacker, trying to identify a red flag or a warning sign that could have prevented another tragedy. Understanding the motives of a lone actor terrorist, a perpetrator who is not directly affiliated with or supported by an extremist group, is particularly challenging. Often, the history of these attackers contains reports of domestic violence, as in the case of Omar Mateen or Tamerlan Tsarnaev, but the connection between lone actor terrorists and gender-based violence has not been previously evaluated in a systematic, dedicated analysis. This thesis addresses this omission by examining the role of gender-based violence and hegemonic masculinity in the radicalization and attacks of post-9/11 lone actor terrorists.
Previous studies of lone actor terrorism have not reached a consensus on a profile of these terrorists but have identified some commonalities. For instance, studies continually show that the majority of lone actor terrorists are male, unemployed, and single and have previous criminal histories. These attributes make it difficult for these individuals to meet standards of hegemonic masculinity—a culturally constructed set of norms that places value on dominance and accomplishment in terms of wealth, heterosexual romantic partners, and control.
This research builds on the work of Mark Hamm and Ramon Spaaij, authors of The Age of Lone Wolf Terrorism, leveraging their dataset of lone actor terrorists in the United States from 2001 to 2016. This thesis expands on their research by examining indicators related to gender-based violence and stressors related to hegemonic masculinity and augments these areas through additional open-source research. Of the 68 lone actor terrorists examined, 28 (41%) of the lone actor terrorists were reported as perpetrators or alleged perpetrators of gender-based violence. An additional four lone actor terrorists reportedly witnessed domestic violence in their homes, committed by the attackers’ fathers. In an examination of stressors related to the performance of hegemonic masculinity, 56 (82%) experienced at least one recent stressor, with 29 (42%) experiencing a stressor related to work or school, 29 (42%) experiencing a stressor related to law-enforcement contact, 26 (38%) experiencing a stressor related to family or romantic relationships, and 19 (27%) experiencing a stressor related to financial stability. Therefore, gender-based violence factors significantly into lone actor terrorism, and combined with the stressors related to hegemonic masculinity, these findings serve as a foundation to improve the understanding of lone actor terrorist radicalization.
Researchers have worked diligently to understand and diagnose why someone chooses the path of terrorism and how an individual becomes radicalized to commit this type of violence. As a result, scholars have developed models that explain an individual’s radicalization through interaction with an extremist group. Lone actor terrorism poses a challenge to this framework because it lacks formal group dynamics. This gap in the research and the increase in lone actor terrorism attacks over the past 18 years speak to the urgent need to improve the understanding of radicalization to prevent future violence. To address this gap, this thesis leverages social identity theory (SIT) in the context of gendered analysis to improve the scholarly understanding of lone actor terrorist radicalization.
SIT explains group interactions through the way individuals construct their sense of self. According to SIT, how individuals construct their sense of self in relation to others explains how groups interact, both in cooperation or conflict. This thesis combines Moghaddam’s staircase to terrorism and Berger’s ladder of identity construction, radicalization models rooted in SIT, with Hamm and Spaaij’s model of lone wolf terrorist radicalization and studies of hegemonic masculinity from Connell and Madfis to create a thematic diagram of lone actor terrorist radicalization in the context of threats to masculinity (see Figure 1).
 Leslie Turk and Liam Stack, “3 Fatally Shot and 7 Injured at a Theater in Louisiana,” New York Times, July 24, 2015, ProQuest; Anderson Cooper et al., “Gunman Opened Fire in a Crowded Movie Theater in Lafayette, Louisiana: Continuing Lafayette Shooting Coverage,” Anderson Cooper 360, CNN, July 24, 2015; Alexa Vaughn, “Idaho Man Arrested over White House Shooting,” Los Angeles Times, November 17, 2011, ProQuest; Mark Hamm and Ramón Spaaij, The Age of Lone Wolf Terrorism (New York: Columbia University Press, 2017), 128.
 Hamm and Spaaij, The Age of Lone Wolf Terrorism, viii; National Center for the Analysis of Violent Crime, Lone Offender: A Study of Lone Offender Terrorism in the United States (1972-2015) (Washington, DC: Federal Bureau of Investigation, 2019), 12–18, https://www.fbi.gov/news/stories/fbi-releases-lone-offender-terrorism-report-111319.
 Hamm and Spaaij, The Age of Lone Wolf Terrorism; Mark Hamm and Ramon Spaaij, “Lone Wolf Terrorism in America: Using Knowledge of Radicalization Pathways to Forge Prevention Strategies, 1940–2013” (dataset, Inter-university Consortium for Political and Social Research, 2017), https://doi.org/10.3886/ICPSR36107.v1.
 For a complete list of sources, see Appendix A.