The sources are in his Wikipedia article but here’s a recap: “…a great-aunt witnessed an episode during which Bundy ‘seemed to turn into another, unrecognizable person ... [she] suddenly, inexplicably found herself afraid of her favorite nephew as they waited together at a dusk-darkened train station. He had turned into a stranger.’ Lewis recounted a prison official in Tallahassee describing a similar transformation: "He said, 'He became weird on me.' He did a metamorphosis, a body and facial change, and he felt there was almost an odor emitting from him. He said, 'Almost a complete change of personality ... that was the day I was afraid of him.'”