He is attempting to transmit a strong non-verbal message. Unfortunately, you are unable to decipher the underlying meaning in his message. Someone who is able to discuss the situation without further triggering his emotions should meet with him in a non-threatening manner and get the rest of the story.
The employees anger may be justified, but perhaps misdirected. Or he may be a ticking time bomb. Someone objective, who is trained in de-escalation techniques, needs to be the one who determines which scenario it is.
Elinor Robin, "The Relationship Mediator," has more than 18 years of experience in mediation while working within the public and private sectors.