I want to let him know I like him without freaking him out...?

I have the mindset of just tell someone how you feel....but there is a guy I am really into that is a bit older than me. I don't kow him a whole lot but there is something about him and i can't get him off my mind. He is leaving in july to go to Madagascar for two years and I can't just not say anything and let him go. How do I tell him without freaking him out?...mind you i don't know him very well. But he is slightly a co-worker and he is a myspace friend.