Hi, here's my theory

Bob Kirkland: He just want to find who Red John is.

Brett Patridge, Sherif McAllister, Reede Smith & Gale Bertram: Members of the tyger tyger organization.

Brett Styles: Boss of the tyger tyger organization. (Episode 7 of season 6 is called "The great red dragon" and i believe that the great red dragon is Brett Styles so maybe in this episode, we'll discover that he is the boss of this organization)

Ray Haffner: Red John (He didn't kill Lisbon cause he loves her, good whistler and blablabla..)