A stranger sent me panties in the mail. What should I do?

I've corresponded several times via email and once via phone with a guy who is interested in dating me. The conversation has never gone beyond the friendly "chit-chat" level. About two weeks ago, he emailed me to say that he had gotten me a Christmas gift. I thought he was kidding. Today, I got a package on my desk at work (it's easy to find my address online) that contained Victoria's Secret underwear. I'm not really sure how to respond. Any suggestions?