How does "Bourne" know?

Abbott used to be director of the Treadstone group of which Bourne was an in. There is no way in Bourne's mind that Abbott could be anything but evil as Treadstone taught Bourne all he knows about killing. Add to this a flashback memory Bourne had about having to kill someone in this same exact hotel room and you can see why he might have been prepared for what he found. It did not help that Abbot was talking about Jason on the phone to the other side. Besides, why would Abbott go there himself? I really did not have to be there at all. he had a personal stake in Bourne being killed.