In the episode when PJ has a flashback, he and his father conned that woman with the sick girl. I believe that RJ has some connection to that girl. That might has sparked a grudge directed at PJ. It would also explain the attachment that RJ had to that blind woman.

I had this theory, that Chirstian Dos Santos was RJ, because he got the devil card in the episode where PJ first met the CBI, but Bruno Heller stated that RJ was on the list, so there goes my theory. Now I suspect McAllister to be RJ. He pretended to have a fear of heights to test if PJ had access to the info from Sophie. When PJ called him, he was right there, just behind him. He knew PJ needed help on the roof. He is the sheriff of a small town, who appeared the least among all the suspects. I bet all of my gummy-bears that he is RJ.