Is anyone going to mention 'echo effect' at some point?
There are multiple ways a single shot can result in more than one noise.
** Echoes.
** The ?Crack? of the supersonic bullet, generally followed by the ?Thump? from the muzzle blast.
** The sound of a bullet or bullet fragment hitting bone, glass or metal.
Meaning that, even in cases where no two shots actually occurred right on top of each other, it should be common for witnesses to report that, by sheer coincidence, two shots occurred almost simultaneously. This is something we should expect.
Witnesses are prone to report phantom pairs of shots. This may be more common with the last shot, possibly due to the longer range of the last shot, or people remembering the shots better once they realized that the noises were gunshots.
Addendum:
I assume there were no large buildings around the shooting site of this video which would provide better surfaces for the muzzle blast to bounce off of, unlike Dealey Plaza. Even so, echoes are still noticeable.