A. It was reportedly a matter of childhood trauma involving Gello's Teddy and a babysitter. Film at 11. In the bunker. Bring your own popcorn.
B. The DRT (Dead Right There) spot on a human is about the size of a walnut. Punching the "apricot", or actually blowing out a section the the spinal cord right below the brain is the only thing I know of that will have the effect of "cutting all the strings". DAMNED hard to do with a handgun that is not touching the right spot on your opponent.
Failing that, your goal is to shut down the CNS by dropping the blood supply. Heart, lungs, liver- but that DOES take time if you are using anything smaller than an anti-tank rocket. The term "Dead Man's Ten Seconds" has been used to describe a person's ability to continue to function AFTER sustaining an injury that will be fatal. The larger the wound channel, and the greater the penetration, that faster the blood pressure is going to drop.
It MAY be possible to knock a person unconcious from the concussion of a head shot (like a boxer landing a solid punch to the temple) but I would not bet on that.
My basic tactic is one that I borrowed from the folks that shoot at armored vehicles- "Shoot until it changes shape or catches fire".
What we have here is... failure- to communicate.