I don't believe it was a co-worker. I believe, and I'm speculating, it was a media member, and then he lied about it to Kim and Terry.
A) Kim and Terry had a consensual workplace relationship; so if RB had one, why would they care? It either wasn't consensual, or it wasn't for the same employer, or it's because he lied to Kim and Terry. Granted if it's the 1st one the other two obviously don't matter
B) Rumors are swirling it's a prominent media member. This makes sense to me. Why? Well, what was a huge reason Murray was fired, and what was a huge criteria and their search for the next GM's? If you don't recall, it was trust, professionalism, and a big emphasis and things discussed in the building staying in the building. Having an affair with a media member really goes against all 3 of those