You can write a counseling that basically states his comment, actions, or behavior have conveyed threats that may violate the UCMJ and endanger others. Then consider recommending the following to the command team: request an investigation through MPI, order a mental health evaluation, and schedule stress and anger management classes.
Before you give the counseling, run it through your 1st and commander for approval.
Last but not least, construct a memorandum for record documenting your actions and recommendations. Include times, dates, and individuals you interacted with and what was said. Odds are there will be no need for this document in the future, but if something happens you have the facts surrounding the actions you took.