I'm dating a guy who claims to be a US Marshal?

He says he's a US Marshal, but I just want to prove behind the scenes if he is or not. I haven't asked him to see his badge..I've been over his house and have seen his fire arm in his holster thaty goes under his clothes..He sounds like he knows evrything there is about it, bcause I've questioned him..He leaves out of town for a few days and comes back (claims to be working, of course) Something just isn't right. I want to know how I can find out if he IS in fact a US Marshal, without him finding out that I investigated him.