Small Wars Journal

Effectiveness of Threat Assessment Models for Lone Terrorists

Thu, 08/13/2015 - 9:07am

Effectiveness of Threat Assessment Models for Lone Terrorists

Rachel V. Neben


Lone wolf terrorists can be difficult to identify before an attack is attempted because the individual is not tied to any specific organization or network. Much of the previous research has gone to understanding terrorist organizations and looking for patterns so that international attacks can be thwarted. Databases such as The International Terrorism: Attributes of Terrorist Events (ITERATE) database and the RAND Corporation’s “Chronology of International Terrorism” along with a few others has given us valuable information regarding terrorism that is threatened from abroad. In 2004, the U.S. National Counterterrorism Center began collecting data on both domestic and international terrorist attacks creating the Worldwide Incidents Tracking System (WITS) (LaFree 60, 2013). All of this data has given the intelligence community valuable information to help create threat assessment models that can be applied to terrorist organizations so that we can be aware of how dangerous an organization may be and actions can be taken accordingly. One piece of information that became quite obvious from analyzing these databases is that international terrorism is on the decline but domestic lone wolf terrorism is on the rise (LaFree 60, 2013).

With lone wolf terrorism on the rise, countermeasures must be created to combat this growing threat. Currently, there is no specific threat assessment model specifically for lone terrorists. Since lone wolf terrorists do not work as a group within an organization, threat assessment model previously created for assessing risk of terrorism, cannot be utilized. On the other hand, risk assessment models that measure risk of targeted violence are utilized on a regular basis and they may be able to be applied to lone terrorists. Borum, Fein, Vossekuil and Berglund refined a threat assessment model that has been “applied to other types of targeted violence in cases of school homicide, domestic violence, stalking and workplace violence, but has not been considered for the lone terrorist” (Zierhoffer 48, 2014). Since these models are not currently being utilized on lone terrorists, studies must be conducted to test the validity of effectively assessing risk of a lone terrorist utilizing models that are currently developed for targeted violence that is not terrorism.

Differences Between Lone Wolf Terrorists and International Terrorist Organizations

Becker defines lone wolf terrorism as “ideologically driven violence, or attempted violence, perpetrated by an individual who plans and executes as attack in the absence of collaboration with other individuals or groups” (960, 2014).  Lone wolf terrorists overwhelming choose targets that the individual would classify as “the enemy” according to their ideology which is not that different from terrorist organizations. For example, Michael Griffin, a radical anti-abortion activist, shot and killed David Gunn, an OB-GYN, to stop him from performing abortions. Another example provided is anti-government activists tend to attack buildings, people or symbols associated with government. However, lone terrorists have to choose easier targets as well such as targets that have less security utilizing easily obtainable weapons such as firearms or homemade explosives which is different than terrorist organizations. They have to choose easier targets because they may not have the capability to execute a larger scale plan (Becker, 2014).

Gruenewald et al. conducted a study of lone terrorist offenders and discovered that two fifth had been previously diagnosed with a mental illness (2013). This is significantly different from terrorist organizations because individuals involved in international terrorist organizations are not known to have any significant mental illnesses. The statistic of mental illness makes including it in the risk assessment model from Borum et al. worthwhile since it can act as a precursor.

Similarities Between Individuals Committing Targeted Violence and Lone Wolf Terrorists

Profiles are also easier to create for a large terrorist organization than for lone wolf terrorists. At this time, there is no one profile that fits with lone terrorists and that may be because studying lone terrorists is a study of outliers much like the study of violent criminals (Zierhoffer, 2014). McCauley and Moskalenko hypothesize that there are two major profiles that can be utilized when analyzing lone wolf terrorists for why they jump from radical thought to radical action: disconnected-disordered profile in which “individuals with a grievance and weapons experience who are socially disconnected and stressed with a psychological disorder” and caring-consistency profile in which “they feel strongly the suffering of others and a personal responsibility to reduce or revenge this suffering” (83, 2013). McCauley and Moskalenko conducted this study by analyzing characteristics of school shooters and assassins as well as known lone wolf terrorists to discover that they tended to have four common characteristics: grievance, depression, unfreezing, and weapons use outside of the military. If a profile of school shooters and assassins can be taken and applied to lone wolf terrorists, one can wager that a risk assessment model that has been utilized for school shooters and assassins can be applied to lone wolf terrorists as well since they are more similar than different.

Borum stated in his policy essay that lone terrorist attacks need to be defined with a “multidimensional approach” to look at not only the radicalization of the individual or how little assistance they had but to analyze how it was planned and executed based off of their personal ideological beliefs (2011). This is more along the lines of the how Borum would conduct a threat assessment utilizing the model for perpetrators of targeted violence. The overlying themes of the questions to be utilized in Borum’s threat assessment model come down to three distinct principals. One is deliberation and planning of the attack. The second is the relationship between the potential attacker, the situation (past or present) and the target. The third is understanding the behaviors of the potential attacker and possible motives (1999). These are the same themes and “multidimensional approach” that are discussed in his 2011 paper regarding threat assessment of lone terrorist attacks.

Threat Assessment

Law enforcement agencies have been utilizing threat assessment models to assess for risk of individuals to become violent for quite some time but the main users of threat assessment models has been the United States Secret Service for prevention of assassination attempts since the early 1990’s. Other national security agencies have conducted threat assessments on groups or individuals abroad but have not applied them to suspects of domestic lone terrorism (Borum et al., 326-327, 1999). Borum et al. goes on to state that one of the difficulties that law enforcement agencies have with applying these threat assessments to individuals is that it requires “a new way of thinking and new set of skills for criminal justice professional” (327, 1999). Because of this, oftentimes, mental health professionals are requested to conduct evaluations and recommend strategies for preventing future violence. As previously stated, lone wolf terrorists have a higher likelihood of having mental illness than international group terrorists, mental health professionals may be the most suited to conduct a threat assessment model that is known to be effective for assessing the risk of lone terrorism (Borum et al., 326-327, 1999).


To assess if previously utilized targeted violence threat assessment models are effective in assessing for risk of lone wolf terrorism. A threat assessment model established by Borum et al and refined for lone terrorism by Zierhoffer has been applied to two known cases of domestic terrorism. Table 1 consists of the questions that were presented for perpetrators of targeted violence and the questions for domestic lone wolf terrorists. In order to complete the threat assessment model refined by Zierhoffer as thoroughly as possible, information was gathered on the individuals for the case study to be able to. This information was gathered from books (such as biographies), scholarly articles, government and law enforcement websites and news reports to get the most well rounded information on each of the individuals.

Table 1: The Threat Assessment Process: Ten Questions Comparison of Questions Developed for Targeted Violence and Terrorism

Case Studies

The threat assessment model developed by Borum et al. as well as the variation to apply to terrorism created by Zierhoffer is applied to the cases of the following lone wolf terrorists: Timothy McVeigh and Theodore Kaczynski. These individuals were chosen for the study because they fit the description of a lone offender terrorist and there is plethora of information regarding their lives and objectives and they have been tried and found guilty of their crimes.  

Timothy McVeigh (The Oklahoma City Bombing)

On April 19th, 1995, Timothy McVeigh parked a Ryder truck with a powerful bomb inside in front of the Alfred P. Murrah Federal Building in Oklahoma City. At 9:02 a.m., the bomb detonated killing 168 people and injuring several hundred more (FBI, 2010). In his official biography, written by Michael Lou and Dan Herbeck, much information was provided regarding McVeigh’s life and motives for the bombings. McVeigh claimed that the bombing was revenge for “what the U.S. government did at Waco and Ruby Ridge.” He was also adamantly in opposition to the actions of the U.S. against Iraq and other foreign nations and he felt that his actions were “morally equivalent”. McVeigh had other plans of violence before deciding to bomb the federal building. He had considered assassinations of various individuals such as Lon Horiuchi, one of the FBI hostage-rescue team that shot and killed Vicki Weaver at Ruby Ridge. He also had plans to assassinate Attorney-General Janet Reno but decided that it would be too difficult (2002).  

Theodore Kaczynski

Theodore Kaczynski, also known as the Unabomber, was the individual who mailed sixteen packages and letter bombs that injured twenty-three and killed three people over eighteen years. Kaczynski was an academic child prodigy and was accepted into Harvard at the age of sixteen and received his PhD at age twenty-five. While at Harvard, Kaczynski participated in the MK ULTRA experiment in which undergraduates were put under extreme stress and their reactions were measured. Immediately after graduation, he became an assistant professor at UC Berkeley. After only two years of teaching, he quit and moved to Montana to live as a recluse while living without technology (Chase 2003). Diagnosed with paranoid schizophrenia, he readily spoke about how technology would destroy nature and control humans (Ibid 1998).

Responses to the 10 Terrorism Threat Assessment Questions

Table 2 shows bullet point responses to each of the 10 terrorism threat assessment questions. The information that was previously gathered was summarized with key points being used to answer the posed questions for risk of committing acts of lone terrorism. All of this information could have been obtained by law enforcement in an investigation of the individuals or provided by family or friends.

Table 2: Abbreviated Responses to Each of the 10 Terrorism Questions

Analysis and Findings

Replicating the study designed by Zierhoffer offered promising results but also many questions. While both studies used Theodore Kaczynski as one of the case studies, this study also conducted a case study on Timothy McVeigh to see if there are similar results. Looking through each question and applying to the individual brought interesting results.

Questions one regarding motivation and question two regarding communication were extremely clear. McVeigh was very open with his anti-government, radical views and wrote and spoke about them often in very public ways. However, as previously discussed, radicalism and extremism does not necessary lead to violence. He did take a step further towards violence by sending letters of recruitment to his plan and spoke with his bomb making accomplice and his brother. Kaczynski on the other hand, was not as open about his anti-technology views but he is very extreme with his views; enough so to leave all technology behind and build his own cabin without electricity and running water and live completely without technology of any kind. He did however, send his family letters regarding his anti-technology views the information was known. That is the only communication he had before the attacks were executed. Once he had started mailing letter and package bombs, he became much more vocal with his view points by demanding his Manifesto be published in its entirety or else he would continue to execute attacks however, this was all done anonymously.

Question three regarding interest in terrorism was less straight forward. McVeigh traveled and worked the gun show circuit and readily spoke about his views at these shows. He went as far as to hand out cards with Lon Horiuchi’s name on it to encourage others to attempt to assassinate him. Kaczynski was not as open with his view points and did not show any interest in terrorism before he started his attacks. Once he started reaching out to newspapers anonymously, he did create a terrorist organization in which he was the only member called the FC (Freedom Club). Question three is much more clear cut to show extremism to violence for McVeigh than for Kaczynski.

Question four for attack related behaviors is also much clearer in regards to McVeigh than for Kaczynski. McVeigh was actively making explosives with others and buying large quantitative of fertilizer to make the bomb used in the attack. He also was encouraging others to assassinate people of interest. Kaczynski, on the other hand, did not show any attack-related behaviors until after he had started his spree.

Question five regarding mental illness did not bring as much information for threat assessment as one would hope. Neither had any previously diagnosed mental illness. The Army did conduct a psychological profile on McVeigh and found him not suitable for Special Forces but he was never diagnosed with any mental illness or receive any sort of treatment. Kaczynski on the other hand had passed a psychological exam during his undergraduate work at Harvard to participate in a psychological experiment but after being arrested, was diagnosed with paranoid schizophrenia. However, his involvement with the study would not have been a red flag and may not have even made it into the threat assessment since it would not have been seen as relevant at the time.

Question six for organization is the only question that would have brought more attention to Kaczynski than to McVeigh. Concern would have been shown about McVeigh since he was ex-military and had received awards for firearm abilities. Kaczynski had a PhD in mathematics, was an associate professor at Berkeley and was fully capable of living completely independent from the outside world; he would have the means and intelligence to pull off a full scale terrorist attack.

Question seven in regards to a recent loss was not nearly as significant for these case studies as Borum states they are for perpetrators of targeted violence. Neither had lost a loved one, a job, a romantic relationship, or experienced economic hardships. Both individuals were loners and had no significant relationships. McVeigh was interested in having romantic relationships but did not have serious loss of one. He was much more voiced about how new gun laws would jeopardize him losing his personal rights. Gambling debt is the closest he had to economic hardship but it not seem to bother him all that much either. Kaczynski willingly left his job at Berkeley to live as a recluse so there was no feeling of loss monetarily. However, he never had any serious personal relationships and he resented his parents for that since they wanted him to excel academically over having interpersonal relationships. This was not a sudden loss though; it was more of a constant sense of loss for most of his life.

Corroboration for question eight and concern of others for question nine brought in some relevant information. McVeigh was very much open with his thoughts and his intention to become violent and he matched that with executing basic plans for assassinations and attempting to recruit others to help him. He also told two others that he planned to bomb a federal building and was actively making bombs for that purpose. However, the people that were close to him, mostly family, did not raise any concern of him. He succeeded in pushing his views on his sister but because she holding similar radical views, she did not voice any concern. Kaczynski did not show any plans for violence or attempt to follow through with them until he started his attacks. He was such a recluse that nobody knew enough about his daily life to be actively concerned about him becoming violent. He did write letters to his family and his family stated that they were concerned about his extreme views and actions against technology. Once the attacks were happening, his family suspected that the anonymous letters could be coming from him and they proceeded to notify the FBI.

In terms of the last question for prevention, it truly depends on when this threat assessment would have been conducted. Some of the items that tipped McVeigh into violent action was finding individuals to help him make explosives. He also started to meet very like minded individuals at the gun shows through traveling with the circuit. For Kaczynski, the tipping point was probably when he moved to Montana to be a recluse. He did not society or individuals to talk rationally with and was able to sit and stew in his own thoughts and loose the closest social ties. For these case studies, this question is where hindsight is 20/20.


Overall, while this threat assessment model may be effective and helpful when dealing with perpetrators of targeted violence, it is not as useful in all cases of domestic lone wolf terrorism. It could still be helpful but if this model was actually being utilized in the case study scenario, Theodore Kaczynski would probably have still committed those attacks. He could have been caught sooner but it is unlikely that it would have prevented any of the attacks. This is mostly because he was so far removed from society that it would be difficult to know that he even existed. Our world is so run by technology and we utilize it so much in intelligence, that he would have flown under the radar for quite some time.

In the case scenario of Timothy McVeigh, the threat assessment model would have been extremely helpful if it had been put into play as soon as he started to become radicalized and working the gun shows. All of his ideological views and some of his assassination plans would have been put into the model and it would have been an open and shut case.

More replications of this study need to be done to really see how effective this model would be but one of the problems that is very apparent is that question number seven would need to be altered for risk assessment of lone terrorism. Based off of the results presented, the two individuals in the case study did not have any recent or significant loss that would have pushed them towards taking action. They had more constant loss over a long period of time and this can also play a toll on individuals.

In deciding how to alter question seven regarding loss, a study should be conducted to look for a common trend between known lone wolf terrorist. If there is a common characteristic or life event, the question could be altered to fit that threat. Some hypotheses, is that it could be an overall anti-social life or a lack of social skills that can make an individual feel alone or like an outsider. This has been a common trend with school shootings and there could be a correlation.

Further research should also been done to see if any of the specific questions could hold more weight than the others. For example, Kaczynski did not have as many key points that would have tipped him off as being at risk of becoming violent but the pure extremism of his ideologies, his anti-social lifestyle and possible paranoia could be significant enough for the model.

It is recommended that this study be replicated with more recent case studies once litigation is complete. The case of the Tsarnaev brothers and the Boston Marathon bombings could be a good study to look at if they are found guilty because they the case is more recent. It would also be very interesting because they are not necessary “lone” wolf terrorists because it is thought that they were working together but they are not known to be linked to any terrorist organization.

While this model shows some promise in terms of its use in assessing risk of lone terrorism, more work needs to be done on it. With more research being conducted every day on lone terrorism as it becomes more prevalent, findings can help morph this model to be more effective and maybe someday used as a standard in assessing risk of lone terrorism.


Becker, Michael. "Explaining Lone Wolf Target Selection in the United States." Studies in Conflict & Terrorism 37, no. 11 (2014): 959-78. Accessed December 29, 2014. Taylor & Francis Online. doi: 10.1080/1057610X.2014.952261.

Borum, Randy. "Radicalization into Violent Extremism II: A Review of Conceptual Models and Empirical Research." Journal of Strategic Security 4, no. 4 (Winter, 2011): 37-62. Accessed December 14, 2014. ProQuest. doi:10.5038/1944-0472.4.4.2.

Borum, Randy, Robert Fein, Bryan Vossekuil, and John Berglund. "Threat Assessment: Defining An Approach For Evaluating Risk Of Targeted Violence." Behavioral Sciences & the Law 17, no. 3 (1999): 323-37. Accessed December 13, 2014. EBSCO Host.

Chase, Alston. Harvard and the Unabomber: The Education of an American Terrorist. New York: W. W. Norton &, 2003.

Ibid; Salley C. Johnson, “Forensic Evaluation,” United States District Court for the Eastern District of California (1998): 40-41,

Gruenewald, Jeff, Steven Chermak, and Joshua D. Freilich. "Distinguishing ‘Loner’ Attacks from Other Domestic Extremist Violence: A Comparison of Far-Right Homicide Incident and Offender Characteristics." Criminology & Public Policy 12:65-91. Accessed January 2, 2015. EBSCO Host.

LaFree, Gary. "Lone-Offender Terrorists." Criminology & Public Policy 12, no. 1, 59-62. Accessed December 14, 2014. EBSCO Host. doi:10.1111/1745-9133.12018

Lou, Michael, and Dan Herbeck. American Terrorist: Timothy McVeigh & the Tragedy at Oklahoma City. New York: Avon Books, 2002.

Mccauley, Clark, and Sophia Moskalenko. "Toward a Profile of Lone Wolf Terrorists: What Moves an Individual From Radical Opinion to Radical Action." Terrorism and Political Violence 26, no. 1 (2013): 69-85. Accessed December 25, 2014. Taylor & Francis Online. doi: 10.1080/09546553.2014.849916.

"Terror Hits Home: The Oklahoma City Bombing." FBI. May 21, 2010. Accessed January 3, 2015.

Zierhoffer, Diane. "Threat Assessment: Do Lone Terrorists Differ from Other Lone Offenders?" Journal of Strategic Terrorists 7, no. 3 (2014): 48-62. Accessed December 14, 2014. ProQuest.

About the Author(s)

Rachel V. Neben is currently perusing a Master’s in Intelligence Studies with a concentration in Intelligence Analysis from American Military University and holds a Bachelor’s in Psychology from California State University, Fullerton. She has conducted research for various non-profit organizations as well as presented research at Psychology research conferences regarding social psychology studies.