Does this incident indicate a duty to warn?

Assessing When to Implement a Duty to Warn

Stan, a retail employee, escaped harm from a building during an active shooter incident by a pair of ethnic minority males. A few months later, Stan began experiencing symptoms of post-traumatic stress disorder and was sent to counseling through his employee assistance program (EAP) when his supervisor noticed an increase in conflicts with coworkers. In the most recent session, Stan became agitated and shouted to the counselor, “I hate those people. I’m going to kill them all,” after which he abruptly left the session.