As I've said time and time again on here, I think some people would be absolutely astonished by how quickly some abusive/manipulative/pathological liar types can come up with their lies .. I know I always used to be when I knew mine. Add to that, as you say, the intruder one is an extremely obvious one to go for .. it wouldn't exactly need a huge amount of effort for someone of that ilk to dream up.
If the gunshots were at about 03:13 or 03:14 and OP called Stander at 03:19 there would be plenty of time to think.