German mass murderers and their proximal warning behaviors.

The main objective of this study was to analyze mass murder cases committed by adults from a threat assessment perspective, and to identify risk factors and proximal warning behaviors. Therefore, court records of 33 German mass murderers between 2000 and 2012 were systematically evaluated. One major focus was the comparison between psychotic and nonpsychotic offenders. Significant differences were found between the 2 groups regarding their choice of weapons, planning behavior, personal crises, personality aspects, and warning behaviors. Nonpsychotic subjects were significantly more likely to evidence pathway warning behavior and directly threaten their targets before the attack when compared with the psychotic subjects. Effect sizes were medium to large. All offenders showed multiple proximal warning behaviors prior to their attacks. Findings are interpreted in light of previous studies and for the purpose of enhancing threat assessment protocols of such persons of concern. (PsycINFO Database Record (c) 2019 APA, all rights reserved)