Maybe I just don't understand shooting at all in this particular situation Gilligan - just seems like there were better ways to handle it BUT I'm going to stop right here turn off the f*****g news regarding and take my 9 o'clock nap. Tom Horman said let the investigation play out. Probably good advice. Happy New Year my friend wishing you a good one.
So, there are a few factors. As noted above, there is literally no way its possible to reliably "shoot to maim". Torso shots are randomly deadly or no, which is why they are trained to shoot multiple shots center of mass, which is not only where most of the important bits are in the human body. Of course one head shot will do it but anyone who has shot, let alone shot under stress will tell you hitting a human head is not easy.
Now, did he have to shoot at all? Even if you posit the threat to him was over, you have to consider this. This woman, when directed to stop and exit the vehicle, had put it into motion. Maybe to flee the scene, maybe to bang a u-turn and come back at them. Its you, and people you love like family at risk. What do you choose? To let her drive off in a 4,000lb weapon?
People on the internet want to ascribe motives and feelings and state things like she was just trying to get home, you could have followed and arrested her there. Maybe she was going to get clear and resume the speed limit..... Maybe she was going to continue in a panic and crash into who knows what.