Mr Shelley, within a couple of hours of the shooting, specifically remembered running into Ms Calvery out at the corner of the park. This is not an incomplete version of the story he would later tell, it is a different story.
Mr. BALL - Then what happened?
Mr. SHELLEY - Gloria Calvary from South-Western Publishing Co. ran back up there crying and said "The President has been shot" and Billy Lovelady and myself took off across the street to that little, old island and we stopped there for a minute.
So all he left out in his testimony was calling his wife. You could say it's a different story, but to me it's just a witness leaving out a minor detail he actually simply might not have remembered on the stand several months later.
I'm not sure where you want to go with this, but I don't see it going anywhere fast.