It's definitely a scam. I used to deal with a lot of Western Union transactions and the you will get MTCN on the spot when you send out the money. He want the item without paying you. If you got time, scam him back.. Make up stories and use your creativity. Here one of the example of to scam the scammer back. This is work of me and my friend last week.

http://petronasadvisorscam.blogspot.com/