I see many theories here which argues that Bob Kirklands identical twin, Michael, is RJ because he killed Jason Cooper... This can't be true for a very clear reason which many surprisingly haven't taken into account:

If Michael Kirkland, Bob's IDENTICAL twin, is RJ, then surely Jason Cooper would recognize him since Cooper WORKED for RJ. So when Michael/Bob asks Cooper if he recognized his face, and he says no, then clearly Kirkland is NOT RJ.

I'm not saying that the guy who killed Cooper wasn't Michael Kirkland, in fact he could very well be, but he is not RJ. But he could possibly be an accomplice to RJ since he wanted Cooper dead.