The Meter Stick

It was halloween night. My friends and I were telling ghost stories. Jake told one about a girl who was murdured and came back to haunt the people who killed her.
We dared Billy to go out to the graveyard and to push a metre stick into a fresh grave. He accepted the dare. We watched him walk away until he disappeared in the dark. We waited inside because we were all too scared to go out. Hours passed and finally the last one of us dozed off.
By the light of dawn, we went to see what had happened. When we saw him all in a heap beside the grave, we knew he was dead. The meter stick was stuck straight into the grave, and also right through the loose material of his halloween costume.
An autospy later showed that he died of a heart attack. With Billy having no heart problems whatsoever, we figured that when the stick went through his costume he took a heart attack from fright, thinking the dead person had grabbed him.