"So many bad things happened in that house!"
Annie made this comment. Also, John said that "after all that has happened in this house". The real estate agent also said that there was panic and it hasn't been forgotten.
Don't these statements imply that other things happened besides the Defeos getting killed? For example, could it be a way of acknowledging the Lutz's ordeal and the events that that happened in part 4 (which I assume takes place right after the Lutz's and before Part 3).