So she didn’t use her own keys, the door was just open a little?
Freegards
If I read right she inserted the key and the door pushed open before trying to unlock.
I figure she had a chip on her shoulder being a woman cop And that if the door was not latching like it should it allowed her to act to fast. I think it was a mistake but no accident because there was no struggle for the gun. I read the story last year when it happened too an there was a line (i’m paraphrasing what I remember) she sat down and said “I’m screwed” after the murder.