He must have a very good pocket-sprung mattress to not notice that there was no girlfriend in the bed when he got himself up from it.
And why would the bathroom door be locked – would you expect your girlfriend/fiancee to lock the bathroom door when there was no else in the house but you?
So he fired four shots through the bathroom door, through a closed door, and 3 of them managed to hit someone who was sitting on the toilet which was in the corner and not at all in a straight line from the door (floorplans are on the net).
If he knew where the toilet was in the bathroom, why would he think that the burglar was sitting on it? Sitting because the shots came downwards apparently, which implies that he had his legs on (or was holding the gun gangster-style above his head).
All sounds too dodgy – I reckon he did it in a moment of rage – maybe brought on by the testosterone they found there.
Anyway he guilty of killing someone.
I doubt it was premeditated though – why the hell would you do that – killing your wife is one thing – but why not just split up with your fiancee?