Here is my view.
I think we have every right to demand perfection of a cop carrying a loaded handgun during interaction with members of the public. It's sort of like I demand perfection from the guy flying my 737 or doing my back surgery.
But I am not naive enough to expect perfection. Cops are human, just like the rest of us. Furthermore, they aren't even the best and brightest of us.
This woman made a huge, deadly mistake, and a guy is dead because of it. There will be consequences to her and to the city that employed her. The family will be paid a lot of money, none of which is enough but its the only method we have. The woman will lose her career, forever, and likely faces a pretty serious criminal charge that will probably lead to a period of incarceration, although she isn't going away for murder, and she will be walking the streets in a few years.
That is just the way it is, nothing more, nothing less.