Does anyone know the name of this play?

I only remember one scene. It was set in a forest, and a load of teenagers were freaking out because they are convinced they killed this boy they were bullying and they're trying to decide what to do.

I think in the end it turns out he isn't dead. I can't remember much else I'm afraid, other than the first scene is a really long conversation where they don't know what to do, and you find out what they did to the boy and decide how to cover up the 'murder'