Just tell it like it is... "son, the cat's dead. Ripped apart it was, lots of blood and guts everywhere. It wasnt a quick death either, my boy. The coyotes teased and tortured him, biting off one limb at a time. They played with his still twitching corpse whist howling at the moon. So, you might as well rewrite your chistmas list, because theres a hell of a better chance of seeing star wars again than what there is our beloved felix. Now, what do you want for dinner?"

He'll appreciate the honesty?