This study is a qualitative and quantitative analysis of written and spoken manifestos authored by lone offenders that planned to or committed a targeted attack (n = 30). The acts of violence were primarily motivated by an ideology or a personal grievance, and occurred between 1974-2021. The main objective of this retrospective study was to examine if a behavior-based threat assessment instrument, the Terrorist Radicalization Assessment Protocol (TRAP-18), could be applied to a thin slice of data using only language evidence compiled by the perpetrator before the event occurred. Findings indicate that 17 out of 18 TRAP-18 indicators (94%) were able to be coded in the manifestos. Proximal warning behaviors ranged from 2 to 7, with an average of 4.5. The average number of distal characteristics was 3.8 across the sample. The most frequent proximal warning behaviors were leakage, identification, fixation, and last resort. The most frequent distal characteristics were changes in thinking and emotion, framed by an ideology, and personal grievance and moral outrage. Further analyses of the manifestos comparing written versus spoken communications, ideologically based versus grievance-fueled attacks, and seven categories of primary motivations, supported the generalizability of the TRAP-18 when applied to only language data. A definition for targeted violence manifestos is proposed and examined within a genre framework. Application to threat assessment and management is discussed. Public Significance StatementThis study analyzed the language of targeted violence manifestos to see if TRAP-18 indicators could be identified in a thin slice of data. Ninety-four percent of the indicators were present, including both proximal warning behaviors, which averaged 4.5 per manifesto, and distal characteristics. A definition for targeted violence manifestos is proposed and examined within a genre framework. Application to threat assessment and management is discussed.

This case study is a detailed assessment of the paranoid schizophrenia and right-wing extremist beliefs of Tobias Rathjen, who amalgamated three low-base rate events: mass homicide, matricide, and suicide. The offender killed nine individuals during a terrorist attack in Hanau, Germany, on February 19, 2020, before murdering his mother and taking his own life. A comprehensive qualitative analysis of primary and secondary sources was conducted, with raw materials consisting of three written documents and three recorded videos, all authored and disseminated by the perpetrator prior to his attack. Open-source data were predominantly composed of the postmortem forensic psychiatric evaluation of the assailant, as well as minor interpellations between the German government and parliamentary groups, and to a lesser extent printed and online articles. We structured the analysis with the Terrorist Radicalization Assessment Protocol (TRAP-18) and found that Rathjen was positive for 94% of the TRAP-18 indicators. The motivations for his acts of violence were multifaceted, but his major psychiatric illness, paranoid schizophrenia with chronic delusions, was central in his progression to become a lone-actor terrorist. In addition to this internally formed psychotic-driven ideology, the perpetrator was influenced and inspired by external (i.e., online and offline) xenophobic and conspiratorial elements that gradually provided a secondary framework for his violent attack. The complex interplay of his delusions, obsessions, and extreme overvalued beliefs-which drove his fixation-reveal the difficulty of clinically understanding such a case, and also the necessity of doing so, to attempt to risk mitigate these types of subjects by threat assessment teams. Public Significance StatementThis postincident research applied a threat assessment instrument to the lone-actor terrorist Tobias Rathjen, who joined three statistically rare occurrences: mass homicide, matricide, and suicide. Ninety-four percent of the TRAP-18 warning behaviors were prevalent in this case, which was predominantly motivated by a severe mental disorder, paranoid schizophrenia, exacerbated by ideological and conspiratorial beliefs from the far-right cosmos.

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