Most Helpful Guy
Hmm, the best course of action, I feel in this case (and remember, please, this is only my idea of what I'd do) is avoid him and treat him with respect as you would do, but do not directly have contact with him. From the details you've said, it would also be best to make it clear to him you don't seek the interest he does. But, not in a mean way. Simply say you would like to remain professional coworkers, and cease any other relationship or form of contact. If he doesn't understand or refuses, he cannot make you do anything. After this, say farewell and cease communication with him. Return to work as usual, and continue to keep a low communication setting with him. Carefully, of course.
Most Helpful Girl
You two clearly want different things, end this before you get hurt and enjoy life, he's not the only guy in the world, keep that in your mind heh a lot of opportunities are awaiting