All weather setting
in heavy use
Join Date: Jun 2007
Location: Near York, UK
Compile a dossier and send it to his employers. Tell him you are going to do this. Don't threaten him with it, simply inform him. Your dossier needs to show his dishonesty. Employers don't need the same level of burden of proof as the Police. His employers will likely take a very dim view of a dishonest security guard. He will know this and may suddenly become more willing to resolve the matter.
I assume you know the security firm he ie employed by rather than just where he works?