She died wearing shorts and a t-shirt. (Possible the same t-shirt she is shown wearing on cctv when she arrived?)
We can assume she didn't put this clothing on in order to get up and go to the toilet. This then raises the question of whether 't-shirt and shorts' is likely to be the nightwear of...
His fate in this dastardly affair will be determined by two pieces of evidence:
1) The position of the holes in the bathroom door and
2) what she was wearing when he shot her.
You see if I'm not right, Watson.