one thing I didn't understand...(spoiler)

I realize that they were hammering the masks into their faces to destroy the demons they had become, and that since both girls went into the fog they both were going to change into demons (basically,) but when the first girl was lying on the alter we saw the face of the guys doing the rituals faces morph into demons. Was this the demons playing tricks on Carmen to make her to think that the ones killing her were actually the demons? That's the only thing I can think of.