My theory is that Bret Stiles killed the two bodies in 1998, and his son - maybe Walter? seen this, left him damaged and he's been copying his dad, that could explain the gap in the murders, Tyger Tyger, Bret's knowledge and lack of fear of Red John, and many other things. It could also be why we can trust the list - because the original RJ was Bret, yet the actual RJ that we know is his son.

(Aswell as the theory being a wild guess, Walter is a guess too, could be someone else)