I bet it isn't even dead. It probably really is an alien and it's just laying there very still, and is waiting for the perfect moment to jump up and frighten everyone.
I heard its been identified as a three toed sloth, and it has no hair because it was rotting in the water for a long time. The kids made up the story about killing it.
So the kids decided to fess up unlike those three portuguese brats back in 1917 who supposedly encountered a radiant woman who told them three secrets about the fate of the earth Hotwater