What if this is an honest (yes tragic) mistake?
What if she was a citizen?
What If I made the same mistake, got off on the wrong floor and thought somebody was in my apartment?
Would it make a difference, if so who and why?
Actions have consequences even if a mistake, you carry a gun around and you have to accept that your choice to fire that weapon has consequences. You can't enter someone's home and call them a threat, at best if you legitimately thought you were threatened your mistake of entering the wrong apartment created the situation that resulted in a loss of life thus we have the charge of manslaughter for those accidental deaths.
If she was a normal citizen she'd have been arrested already.
You'd be arrested and in jail (or on bail).
The color/gender of the victim wouldn't make any difference but in the case of our slanted legal system the consequences for officers (on and off duty) see to be "different" even when there isn't any official justification (in the eyes of humanity) for their actions.