Yes there was. According to John Connally. On the CBS news special "The Warren Report", Connally clearly states that just after the turn onto Elm Street he heard a rifle shot, and turned to his right. This statement alone proves there was an early shot. He said he didn't hear the shot that hit him, which would be the 2nd shot, which struck both he and President Kennedy. He heard the 3rd and final shot and felt the results of it. So Connally heard a total of 2 shots. Furthermore, evidence that backs up Connally's statements of the earlier shot are the quick, 1/4 of a second head turn he made. Connally was looking to his right, turned to look to his left, and SUDDENLY snaps his head back to his right, and his head remains in that position until he changes his position for the first time since head turn to the right in 1/4 of a second in frame 224 pf the Zapruder film. He gaze to the right is transfixed until his face becomes distorted when he's struck around frame 222. This is all captured in the Zapruder film.
I've been waiting to see if any of the LNs had a theory as to why Clint Hill specifically, but also other passengers in both limos, didn't seem to have either heard or recognized the first shot for what it was. I have speculated the roar of the accelerating motorcycles could have disguised the sound of that first shot but I wondered if others had different theories for that.
