This is not a theory but more of an observation. Based on PJ recollection, we can see that he enters his home but there is not sign of broken entry. In fact in his memory, he only discovers his wife and child dead body once he enters the room.
Would this be a clue that his wife might have known RJ or that it would be someone she would trust(Law enforcement officer) to let that person in. Also it would be explain that RJ knows about the childhood memory if it were someone she knew but not so much a a law enforcement officer.  Was it ever explained how RJ entered PJ's home? 
Let me know what you think.