Aiming for center of mass is a pretty universal bit of firearm training. Doesn’t excuse their reaction, but it is what you should be doing if you’re gonna fire on someone. Going for legs or arms or a headshot means you’re more likely to miss.
Since Sonya Massey was shot in the head, that implies three things:
There was an exchange of gun fire and Sonya was caught in the crossfire.
The police showed up and started shooting randomly, killing Sonya.