yesterday I thought it must be Stiles but now I beg on Haffner after rewatching the Episode where Rebecca killed Bosco and was poisoned by RJ. The man who came along in Police uniform fits Haffner...
After re watching Episode Litttle red book Haffner asks Cho if PJ is smarter than Cho and if he is smarter than him...Then he manipulates Cho by offering something he wants (to have his Job back-and asks for doing something for him (looking for PJs attempts to cheat on Haffner).
His past fits with beeing at the red barn at the right time. he is into visualize and tries to connect to Lisbon...)
 I think he is smart enough to make People work for him.
And watching him and PJ sitting on the Sofa in front of Bertram makes them look like" fearful symmetry".
His Alias is similar to his real Name (Roy/Ray) and he fits also  to the description of Rosalind Harker.
The murdered happy Memory of PJ is easy to access- when he was devastated after the killing of his Family it might be a good therapeutical Access to evoke happy memories, so I think it´s easy to know  from a coworking-therapist for example.
If it´s Haffner it´s most easy for him (who´s subject was observing..) to Install a camera or get any Access to Patricks "Office".
Like the Video tape of Lorelai murdering the woman- there was a tiny camera in a clock...So it´s easy to know the names of the list without the mind intruding staff and so on.
Patridge is way to childish and not  masterminded enough  to make anyone of the man work for him (like Lennon.Please! Does anyone believe Lennon is working for him???)
And he doesn´t seem to have enough power to handle Lorelai.