A post yesterday said folks in "Edens" have a good idea. McFadyen's was the only other room searched. Unless, that was a reference to the lacrosse players in Edens.
Probably because of the questions the police were asking during their "visit" to Edens dorm. The police were reported to be asking the other students in the dorm questions regarding whether certain people were or were not at the party.
The police were probably focusing their question on one or two names (the guy the AV is "90% sure of") and that's how the Edens folk got the idea of who it is.