Hefner, thinking the call a prank, would not come to the phone at first. No one knows for certain what happened that horrible day, but there are clues. He left the impression that they were on amiable terms. The pair said they went upstairs to watch TV, and said they just assumed Dorothy and Paul had made up and were downstairs in his bedroom. Since the murder, not much has been made of this film, probably because it contained unpleasant overtones of bondage.
Dorothy Stratten Crime Scene: What the Coroner Found | eldb.net
Since they heard no sounds, they assumed he wanted privacy. She cried in private. He was found face-down lying parallel to the foot of the bed. The best known is Star 80 , with Mariel Hemingway as Dorothy. He then called Bogdanovich. You can read that seminal Village Voice article here; it was called Death of a Playmate.