[mb_]

Can't really answer your first question cause there's a lot of ways that he could have known.

But for your second question, when Virgil followed Quinn to meet up with Dar Adal, Saul confronted him and asked who he is and he said "he's one of mine". He then asked Estes what he's doing there and he told him "he's here to kill terrorists" and that he wasn't really an analyst.