does true evil shift before the eyes?

I was watching an interview with Chris Carter where he was talking about some episodes of the X-files and he mentioned something fascinating about the inspiration behind of the episodes. The episode was about a run of the mill serial killer who appears as a shape shifting demon in the eyes of his victims, Chris said that this came from sightings of people who were in contact with Jeffrey Dahmer.

I tried to find any reference to this and was unsuccessful but the mere thought of this is chilling.

I don't believe he mentioned if it was would be victims who reported this or acquaintances. Considering the duality of people like this, if it was the would be victims could it be some sort of a defense mechanism or a real manifestation of true evil?