If the 6th floor gunman (or rifle demonstrator?) at TSBD SE window was hiding out of LOS until after JFK limo has fully turned on ELM st and has passed by the window and past the traffic light, then IMO there is only approx about 3 to 4 sec until limo is at the Z160 location on Elm St.
IMO it’s therefore more probable if there was a shot fired as early as Z160 by a lone shooter from the TSBD SN window that it was an accidental unaimed shot DURING his effort to get himself onto crouched kneeling firing position.
Seated on the box on the floor and sitting up straight, he was out of the line of sight. Just leaning his upper torso forward (while staying seated) he was in a good position to aim and fire as the limo traveled away from him down Elm Street. The seated position is the most stable one and doesn’t require any awkward, time consuming movements to get into a kneeling position. Therefore I believe that he stayed seated on the box for the shooting.
I don’t believe that he would have had an opportunity to practice aiming at moving vehicles in the kill zone with the actual rifle without risking being seen aiming the rifle and possibly bringing unwanted attention to himself. But it is reasonable to believe that he could have mentally practiced doing this. He could have kept the rifle at his side and low enough that it could not be seen from the viewpoint of the bystanders outside and below until the limo traveled into his selected kill zone.
When the time came to pick up the actual rifle and aim, I believe that it was most likely the first time he did this with the rifle actually in hand. The pipe (appears to me to be an electrical conduit) closest to the window would have been very close to his left elbow position if he was seated and aiming down Elm Street. However, he most likely had not realized this due to a lack of actual practice with the rifle. It is possible that his left elbow could have collided with the conduit while he was bringing the rifle up into position and starting to aim. If this happened, the elbow collision might have caused an inadvertent shot to be fired before he had fully aimed the rifle.
A somewhat similar scenario is possible if he was aiming and tracking the limo as it passed right below the window. However, in this case the top box in the stack below the window would have been the item in the way of the rifle barrel. Some people believe that they see some movement in the window in the Hughes film. So I don’t rule this possibility out.
However, I believe the most likely theory to be the first one in which the conduit is the cause. One reason for this preference is the bullet marks on the manhole cover on the south side of Elm Street and the curb near the position of Tague. And Tague’s injury of course.
Then again, Max Holland’s demonstration regarding the spent shells distribution is interesting and coincides with the shot being made while the limo is below the traffic signal (from the sniper’s nest viewpoint). If this is the reason for the spent shells distribution pattern, then interference from the top box could be the reason the shot misssed (in lieu of it hitting the traffic signal).
