My heart's breaking for my boy.

So, Zach came home from school totally heartbroken today. Apparently, during recess Zach's good friend since school last year told him that he's not only not Zach's friend anymore, nobody else is, and nobody likes him, and that he couldn't play with them. I've been trying to convince him that this isn't true, but Zach just doesn't believe me. Obviously, to him, since this mean little boy told him this, it must be true. I never knew kindergarteners could be so hateful to each other. Especially since he's been friends with this boy for almost two years now. Zach was so happy when this boy got transfered to his class because nobody else from his class last year was in his class this year. Now his heart is broken and he truly believes nobody likes him.