In several camera shots of Peter's bathroom, including camera angles in the bathroom, the shower is directly in front of the door. When Burt discovers Peter dead in the shower, the camera shows the sink/counter in front of the door.
When Mrs. Fine and Peter are in Peter's bathroom, the wall between the toilet and shower is about chin high on Peter. But when Peter is murdered, this wall is now so high that it is taller than Peter. Also, the shower curtain rod goes from being "C" shaped (both ends attaching to the same wall) to being straight (connecting to the opposite walls of the shower).