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.
The other agents in the followup car heard three shots despite operating under the same disadvantages vis-a-vis the motorcycle engines, so I'm not sure if that's the answer.
Hill heard the first shot.He also heard the second shot.He doesn't remember hearing the third shot as he had a lot on his plate at that moment, including stopping Jackie from jumping off the back of the limo.
At Z312 Hill was galloping & was level with the front left wheel but somehow did not hear Hickey's burst of 4 or 5 or 6 shots, less than 3m from his right ear.
