Episode 6x18, Behind the red curtains.. Kirkland asks to Lorelei's surviving victim (cant remember his name) if he recognizes him and that he is his friend.. And then kills him! Though it makes me think he his RJ, it would be way too obvious!
So I'm thinking that he is doing the job for someone else.. And do you remember few episodes before when Kirland and Bertram in the office say that they can't trust anyone, referring to Lisbon?
So RJ may be Gale at the end!