The coven likely caused Rosemary’s friend Hutch who knew too much about this history of the building and its dark past to die. Rosemary’s predecessor (Terry) killed herself by jumping out of the Castavet’s apartment.
Yes, Hutch was killed by the coven. Guy, Rosemary’s husband, came home unexpectedly from rehearsal when Hutch was visiting with Rosemary and Hutch seemed to be catching on to what was going on. When Hutch was leaving he was missing a glove, which Guy had taken to give to the coven to cause Hutch’s demise just as Guy had taken the tie of the man whose part he wanted to get that caused the man to go blind.