In 2x8 (His red right hand) we learn about another operative for RJ. I suggest watching this episode if you haven't seen in. Reveals that RJ is in fact human and capable of making mistakes.

At the very end of the episode, RJ (we presume because Rebecca smiles lovingly at a character walking towards her) kills Rebeca. The clip is below.

http://www.youtube.com/watch?feature=player_detailpage&v=1otRlA3PedI#t=82s

Most importantly, at 1:25 you can capture the back of the presumed RJ head. Dark hair, cut short. He is dressed in the same uniform as the other officers. You would need to presume then any of the suspects that would have "normal access" there would be recognized by other employees. And therefore would be suspicious if they were in a officer uniform. (i.e. partridge or bertram). 

The most likely case would be Kirkland.