Daisy, you didn't say how or where you met him or if you see him regularly in the course of your day or you have to make a point to see him. I have been in the same situation. All I can say is be sure you do not do anything to lead him on or give him false hope because that will hurt him more.

If you cannot help but see him (he works with you, rides the same bus, etc) be nice and friendly when you see him but do not make it point to get too close to him. If you do not see him unless you make an effort, don't see him. He will be lonely regardless because he cannot have a relationship with you. The less his thought dwell on you the more likely it will be he meets someone else.

Formerly I would have tried to help him and ended feeling trapped in a smothering relationship. I had to tell myself I am not the saviour of the world. He will get over it or he won't. He has probably been a loner and lonely most of his life. It is not my job to fix him.