We know from the police presser that they have some video of the perp, some of which they have released, and they identified the time the victim arrived because the cameras captured her coming into the building.
They said the murder was not captured on the cameras, and so we know it did not occur in those hallways that can be seen in the videos.
They also don't make any mention of seeing the perp leave the building, so that leads me to believe the murder happened in another part of the building, away from any hallways with cameras, because if it had happened in the room with the Dutch doors, for instance, they would have seen him leave that room afterward.
Interesting.
Maybe no cameras in the ladies room??