And now I know...Whodunnit

The killer was revealed in Sunday night's fnale.  Three contestants remained, a final quiz that involved a lot of running...it was an exciting finale.
Except the part where the killer is revealed.  That part still confuses me.  The killer was a castmate who was playing the game all the way through with the rest of the contestants?  The killer didn't know how the murders were done, but only knew that he or she was the killer?  Was the killer an employee then?  Or a contestant they selected randomly?

I felt bad for Lindsey who was suspected to be the killer most often, and the one who knew it was Chris the whole time.  She came in second - the last victim.  But, Cam played a good game so it's fine he won.

Oh well.  It was a fun enough show. I'll leave the final word to Andy Dehnart at Reality Blurred, who writes better than I do, and I agree with what he says.

P.S.  I'm sorry I thought you were the killer Melina!