Hi, I am a Cancer, but I am also a woman. That being said, I know Cancer people pretty well man or woman. I think the men are mirrors of the women just different gender.
Do you have reason to believe that he is intrested in you? Are you sure he is intrested?
As a Cancer alot of things make me emotional. If he considers you good friend and you had a good relationship he is sad to see you go. It feels like "abandonment" in a way. We cling to people(I hate the word cling) When we find some one we mesh with we try to hold on cause not many can mesh well with us.
I hope this helps a little, if not let me know and I'll clarify better. Happy travels, good luck.