Paul Gill

Several months prior to Anders Breivik’s attack in Norway, researchers at the International Center for the Study of Terrorism (at Pennsylvania State University) had begun work on a project entitled “Tracing the Motivations and Antecedent Behaviors of Lone Actor Terrorism”. This one-year project was funded by the Department of Homeland Security’s Science and Technology Directorate, and the effort was coordinated through the United Kingdom’s Home Office in conjunction with DHS.

Based on an extensive analysis of 119 lone actor terrorists across a mixture open-source material, the report contains important insights into who the Lone Actors are, what they do, and ultimately what an analysis of their behaviors might imply for practical interventions aimed at disrupting or even preventing attacks. The researchers – Paul Gill, John Horgan and Paige Deckert- came to seven major conclusions.

Finding 1:
There was no uniform profile of lone-actor terrorists.

Although heavily male-oriented, there were no uniform variables that characterized all or even a majority of lone-actor terrorists. The sample ranged in age from 15 to 69. Half were single, 24% were married and 22% were separated or divorced. Twenty-seven percent had children. Educational achievement varied substantially. While 40% of the sample was unemployed at the time of their terrorist attacks or arrests, 50% held jobs and 10% were students. Twenty-six percent had served in the military. Finally, 41% had previous criminal convictions, 31% had a history of mental health problems and 22% had a history of substance abuse.

Finding 2:
In the time leading up to most lone-actor terrorist events, evidence suggests that other people generally knew about the offender’s grievance, extremist ideology, views and/or intent to engage in violence.

Indeed, most of the variables pertaining to this section occurred far more regularly than any of the socio-demographic variables outlined above. This suggests that lone-actor terrorists should largely be characterized by what they do rather than who they are. For a large majority (83%) of offenders, others were aware of the grievances that later spurred their terrorist plots or actions. In a similar number of cases (79%), others were aware of the individual’s commitment to a specific extremist ideology. In 64% of cases, family and friends were aware of the individual’s intent to engage in a terrorism-related activity because the offender verbally told them. These findings suggest therefore that friends and family can play important roles in the early detection and prevention of plots. In 58% of cases, other individuals possessed specific information about the lone actor’s research, planning and/or preparation prior to the event itself. Finally, in the majority (59%) of cases, the offender produced letters or made public statements prior to the event in order to outline his/her beliefs (but not his/her violent intentions). These statements include both letters sent to newspapers, self-printed/disseminated leaflets and statements in virtual forums.

Finding 3:
A wide range of activities and experiences preceded lone actors’ plots or events.

Half of the sample changed address at least five years prior to their terrorist event planning or execution. Of the 40% who were unemployed, 27% had lost their jobs within six months, and a further 16% between seven and twelve months before the event. On a related note, 25% experienced financial problems. Thirty-three percent of the offenders were characterized as being under an elevated level of stress due to a number of reasons. Fifteen percent subjectively experienced being the target of an act of prejudice or unfairness, 19% subjectively experienced being disrespected by others and 14% experienced being the victim of verbal or physical assault. A fifth of the sample converted to a religion before engaging or planning to engage in an event. Thirteen percent noticeably increased their physical activities and outdoor excursions.

Finding 4:
Many but not all lone-actor terrorists were socially isolated.

More than a quarter of the sample (27%) adopted their radical ideology when living away from home in another town, city or country. Thirty-seven percent lived alone at the time of their event planning and/or execution, and 53% were characterized as socially isolated by sources within the open source accounts we coded.

Finding 5:
Lone-actor terrorists regularly engaged in a detectable and observable range of behaviors and activities with a wider pressure group, social movement or terrorist organization.

Approximately a third of the sample had recently joined a wider group, organization or movement that engaged in contentious politics. Just less than half (48%) interacted face-to-face with members of a wider network of political activists, and 35% did so virtually. In 68% of the cases, there is evidence to suggest that the individual read or consumed literature or propaganda associated with a wider movement. Fourteen percent previously engaged in fundraising or financial donations to a wider network of individuals associated with either licit pressure groups or illicit groups who espoused violent intentions. One in six (17%) sought legitimization from religious, political, social or civic leaders prior to the event they planned.

There is evidence to suggest that in 17% of the cases there may have been wider command and control links specifically associated with the violent event that was planned or carried out. In approximately a third of the cases (35%), the lone actor had tried to recruit others or form a group prior to the event. In 24% of cases, other individuals were involved in procuring weaponry or technology that was used (or planned to be used) in the terrorist event but did not themselves plan to participate in the violent actions. In 13% of cases, other individuals helped the lone actor assemble an explosive device.

Finding 6:
Lone-actor terrorist events were rarely sudden and impulsive.

Training for the plot typically occurred in a number of ways. Approximately a fifth of the sample (21%) received some form of hands-on training while 46% learned through virtual sources. In half the cases investigators found evidence of bomb-making manuals within the offender’s home or on his or her property. The fact that strategic and tactical planning goes into lone-actor terrorist events is demonstrated by the finding that 29% of offenders engaged in dry-runs of their intended activities.

Finding 7:
Despite the diversity of lone-actor terrorists, there were distinguishable differences between ideological subgroups.

  • Al-Qaeda-related offenders were younger and were more likely to be students, seek legitimization from epistemic authority figures, learn through virtual sources and display command and control links. They were less likely to have criminal convictions.
  • Right-wing offenders were more likely to be unemployed and less likely to have any university experience, make verbal statements to friends and family about their intent or beliefs, engage in dry-runs or obtain help in procuring weaponry.
  • Single-issue offenders were more likely to be married, have criminal convictions, have a history of mental illness, provide specific pre-event warnings and engage in dry-runs. They were less likely to learn through virtual sources or be depicted as being socially isolated.
This entry was originally posted in Extremis Project.


Dr. Paul Gill is a lecturer in Security and Crime Science. His research examines terrorism: its causes, patterns and the actors that perpetrate terrorist attacks. His currently published research demonstrates the heterogeneous profiles of terrorists, their developmental pathways into terrorism, how terrorists fit into a wider structure and how particular group influences condition individuals to engage in acts of violence.

Previous to joining UCL, Dr. Gill was a postdoctoral research fellow at the International Center for the Study of Terrorism at Pennsylvania State University. He has previously managed projects funded by the Office for Naval Research and the Department of Homeland Security. These projects focused upon various aspects of terrorist behavior including the nature of malevolent creativity, terrorist network structures, terrorist leaders and lone-actor terrorism.

His doctoral research focused on the underlying individual and organizational motivations behind suicide bombing. This piece of research won the Jean Blondel Prize for the best Ph.D. thesis in Political Science in Europe for 2010.

Dr. Gills holds a Ph.D. in Political Science, an M.A. in International Relations, and a BSocSc(Int) from the School of Politics and International Relations in University College Dublin, Ireland.

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7 Responses to Seven Findings on Lone-Actor Terrorists

  1. suhaib says:

    Good research I am a researcher of terrorism and find out more than 100 reasons of terrorism i want publish my reasearch through ICST.

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  5. […] of the individual’s commitment to a specific extremist ideology. In an astonishing 64% of cases, family and friends were aware of the individual’s intent to engage in a terrorism-related activity because the offender verbally told […]

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