No mortal can hold a pistol perfectly still. Some people are more trained and coordinated to approach that goal than the rest of us. The gun is still moving a little or a lot as the gun fires. The dot or sight will appear to stop for an instant as the shot breaks. We see this picture in our mind a fraction of a second after it has happened.
Light strikes the rods and cones in the back of the eye and a chemical reaction occurs.
The nerve impulses from that chemical reaction are transmitted to the optical nerve, also by a series of chemical reactions in the nerve cells. One notes that these biochemical reactions take a finite and actually rather long time. In bullseye as well as other shooting disciplines, this concept is extremely important. Quite simply, one living in the past can not have an effect on the present. The only decision the conscious mind can make is to stop the shot from firing.