A good "hypothetical".
You react as you train. So, unless you train in thinking "shot placement" within a millisecond or so, you are going to shoot how you perfect practice.
In laymen's terms, the question is academic and the common sense response is that if you do train to shoot the pressure points, the bladder, the base of the neck (meaning wherever you want to shoot), you will make that decision instantaneously.
Assistant squad leader shot dead at a distance of 4 feet in the chest with a .308 round. Was he dead when shot by hydrostatic shock? No.
The points are: 1. a person in movement may still be in movement despite a "kill shot"; 2. let us know after the encounter.
A base of the throat shot is good, a head shot is good, a bladder shot is good, a shot that takes out a leg is good.
How many people do you know train to shoot this way? I know very few.
People shoot "center mass" because they are not taught shot placement. Center mass is the largest target on the human body. I had a foreign country SF Lt. Col. complain that his people did not shoot for exposed legs, elbows, arms. Well, they simply weren't trained to do it. Then his team was trained to think in terms of cutting and indexing so that they weren't hesitant to shoot an exposed elbow. Just think if a guy is trained to think "center mass" "center mass" and then has to shoot and center mass is not exposed!
Frankly, I am going to shoot from wherever my handgun or file is located if the person is close in. If it is light, it is the base of the throat. If it is dark, lower down. None of the "two to the chest, one to the head" (garbage). Just keep firing until the threat is terminated.
There is nothing to require you to be static in your hypotetical, so MOVE! Yes, you can be trained to shoot handgun, rifle, shotgun and/or machine gun while on the move. Once I received permission to shoot the 100 yard standing leg at a DCM match while walking. Isn't this what you really want to do in your life and not stand static and let some one shoot back at you?
If all you are ever taught or can do is shoot center mass, then do it.
I give you a story. I was taught to rock, draw and shoot at close distance. It really bothered me. So, I thought outside the box and asked a san soo master who was a shooting instructor to demonstrate what he would do. He moved at an angle, drew and shot the target as he raced by with strong arm retention. When you reflect on how few people think in those terms, perfect practice that way, and are open in their thinking, you realize how much we all have to learn.
I would have sent this as a private email, but it is not allowed on this board.
By the way, assume it is light. If you shoot for the base of the throat and hit a bit high, low, to the right or the left, what do you hit? Is there body armor or heavy clothing at those points? Is center mass where body armor or heavy clothing would be?