I'm thinking that EC was sleeping and XK was awake. I would think XK's DD order would indicate if he was awake along with his phone records. If she ordered food for him, then he probably was. If not, I would assume he was sleeping. But maybe he just didn't want anything. Maybe when she said "there's someone here", she was saying it out loud and trying to wake EC at the same time. Being that he's a good size gentleman, I would think if he was alert, he would have come out to check instead of XK getting up.
Makes more sense that BK went straight to the 3rd floor. Too much noise was happening with the dog etc, XK heard it, and BK heard or saw movement on the 2nd floor when he came back down and then attacked XK and EC.
(side note: I see you used XR to refer to Xana. So many times when I was writing, I wanted to type XR too.
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MOO