I always come back to the state having to prove it was not an accident. A certain amount of negligence occurs in virtually all accidents.
I also think (solely my opinion) is that the accident occurred when she actually pulled the trigger. Both weapons had triggers. If I understand correctly you are trained to fire once with a taser and twice with a Glock. (I could be wrong on this as I am not a cop) She fired once.
“I always come back to the state having to prove it was not an accident.”
They don’t have to prove it wasn’t an accident. They only have to prove culpable negligence on her part.