Understanding the behaviors and stressors of active shooters is critical to threat assessment teams as they evaluate persons of concern. Yet research focuses on those who commit an attack, which means little is known about how active shooters differ from other high-risk persons of concern referred for assessment. Sixty-three active shooters were matched on age and gender to high-risk persons of concern assessed by a federal law enforcement threat assessment team. Variables measuring past behavior, internal stressors, and behaviors that drew the concern of others were analyzed. Logistic regressions highlight that concerning persons’ behaviors appear more worrisome than active shooters’ behaviors. Active shooters were less likely to have someone concerned about their anger as compared to persons of concern. Conversely, active shooters were more likely to have experienced a humiliating event. Results are discussed with a focus on being operationally useful. (PsycInfo Database Record (c) 2020 APA, all rights reserved)