I still go with Max Holland when he says the first shot occured about 1.4 seconds before Z133.
If the first shot was the one that injured James Tague, it had to lose its copper jacket somewhere along the way, probably when it glanced off the traffic light mast arm.
Hinkley (sp?) bent over and looked at something on the ground. His attemtention could have been drawn to the falling debris from that impact.
-- MWT 
I think Hickey was probably looking at tires for evidence of a blowout after hearing the loud bang. I have a theory that LHO was positioning the rifle and intended to wait to fire until just after JFK emerged from the other side of the tree (from the sniper's nest view). But, while moving into position, his left arm hit the electrical conduit between his position and the window frame and this unexpected collision caused him to inadvertently fire the rifle before he could fully position and aim it. The bullet could have hit the corner of the concrete pad where DPD Foster found a mark. There is also a furrow in the turf nearby. The copper jacket could have separated from the lead due to that impact and the jacket caused the furrow. Some or all of the remaining lead bullet could have continued and struck the curb near Tague's position. Just a theory, but I don't know of any conclusive evidence that says it is impossible.