The whole twin thing, plus the elluding to the bob murder was weird (rigsby talking to that detective), and PJ getting every suspect in the room. Not sure how PJ could convince RJ to meet out in a cabin out in the middle of no where. 

I suspect that RJ is either Bob or Patridge, only from the fact of the explosion. Perhaps RJ kills all the suspects which is when we learn who RJ truely is. For the episode great red dragon?