I believe communication is a good idea in all but one type of case. If you have a reasonable suspicion that criminal activity is involved, then early notification of law enforcement is important.
Years ago, I had occasion to fire an employee because he threatened others with workplace violence. I was concerned that he might be armed at this final interview, so I was armed (concealed) as well.
Thankfully, the interview went smoothly and uneventfully. Looking back on this years later, I cannot imagine what I was thinking. I have since learned a lot about the criminal laws of self defence, and this would have been a very dicey case - at best! At worst, I would not be writing this post. I should have advised law enforcement of the matter and stepped away.
In subsequent criminal matters, I have simply called the police.
Any other anecdotes of this kind of situation?
NOTICE: This comment was moved from an existing discussion: Writing Up Techs, What To Do When Employees Cost You Sizable Sums?