Disgruntled Former Employer 

A former employer who is furious at you for leaving before they could trump up a reason to fire you. Usually found in companies that believe they own their employees.

Bob: "I'm still getting threatening emails from my old boss."

Dave: "You should call the police; you have a Disgruntled Former Employer."

Disgruntled Former Employer by Murray Rothbard April 5, 2008