My thoughts about the ending (SPOILERS)

I have to say I'm a bit confused as to whether it was Ethan possessing Robin or if it was the demon. Robin was possessed when she went back into the little room in the church to sign her name, but she didn't sign Robin... she signed "Ethan was here." That gave me the impression that Ethan was in possession of Robin's body. Perhaps Ethan himself was a victim of the demon when he went to Covington to end it all, and was now the demon's pawn, being used to torture and kill Robin and her so-called friends (I say so-called because damn, they sure were nasty little brats to her).