Revealing mistake: When Emma hits a man using the flower pot, Angela Lansbury's stand-in is a much younger stunt double.
Revealing mistake: When the first scene at Emma's hideaway was shown, obviously the two characters Emma and Jessica were filmed seperately on the couch and then the film was put together (as both are played by Angela Lansbury). However Jessica did a lot of moving while she was talking, so Emma was looking straight across at where she had been, despite her bending down while she talked.
Revealing mistake: Kat pumps her shotgun several times with no shells coming out.
Revealing mistake: When Jessica visits the basement, there's plenty of light everywhere. She then turns off the light, but there's still plenty of light. However, when Adam Frobisher shows up half a second later, the whole place is now in darkness to allow for all the mystery and the intrigue.
Answer: In a flashback scene, it was shown that he had a violent temper, so it stands to reason that he finally killed her in a fit of rage.