What does Simon find when he finally reaches the beast in Lord of the Flies?

Simon discovers a fallen fighter jet pilot who has gotten
tangled in the trees when he climbs the hill. Since the wind periodically fills the
parachute dangling from the branches, the other boys thought this was a beastie
expanding in preparation for attack. However, Simon finds out the truth, untangles the
dead man and allows him to float out to see.

The irony of
this whole situation is that Simon was on his way to tell the boys that there was no
beast and they were safe, when the boys spear him to death thinking he was the beast
come to get them.