Presidential aide Kenneth O’Donnell, who was riding in the Secret Service follow-up car directly behind President Kennedy’s limousine was also aware of shots from the front.
In the autobiography of the late Massachusetts Congressman Tip O’Neill, O’Neill writes, “I was surprised to hear O’Donnell say that he was sure that he had heard two shots that came from behind the fence.”
"Man of the House" was not a bona fide autobiography. It was written by professional ghost-writer William Novak, using audiotapes made by O'Neill. One can imagine O'Neill in the comfort of his home with an Irish whiskey waxing poetically with a bit of blarney added. I believe the book drew some criticism from people who said what O'Neill claimed about them didn't happen. It was less academic history and more political anecdote.
“‘That’s not what you told the Warren Commission,’ I said.”
“‘You’re right,’ he replied, ‘I told the FBI what I had heard, but they said that it couldn’t have happened that way and that I must have been imagining things. So, I testified the way that they wanted me to.’”
O'Donnell doesn't seem to merely "go along" with a "narrative"; in 1964, he's laying out the rationale for what he heard:
Mr. SPECTER. And what was your reaction as to the source of the
shots, if you had one?
Mr. O'DONNELL. My reaction in part is reconstruction---is that they
came from the right rear. That would be my best judgment.
Mr. SPECTER. Was there any reaction by any of the other people
around in any specific direction?
Mr. O'DONNELL. The agents all turned to the rear. I would think,
watching the reaction of the President when the shot--the first
shot hit--that it would be automatic it would have to have come
from the rear. I think any experienced agent would make that
assumption immediately.
Mr. SPECTER. And was the reaction of the agents which you have
referred to as coming from the rear, to the right rear or to the left rear?
Mr. O'DONNELL. The reaction I note would be right rear. And, again,
looking at the manner of the President's movement, I would think
you would have to feel the thrust of the shot was from the right rear.
Now O'Neill said he got Dave Powers to "confirm" the meeting but we don't know to what extent. Powers himself was a "shot from the front" fellow, suggesting the Underpass:
"My first impression was that the shots came from the right and overhead,
but I also had a fleeting impression that the noise appeared to come from
the front in the area of the triple overpass. This may have resulted from my
feeling, when I looked forward toward the overpass, that we might have
ridden into an ambush."
-- Affidavit, May 18, 1964
So if "two shots that came from behind the fence" is accurate, it represents a change as to the source of shots for both men. By 1968, when the dinner meeting was said to have taken place, the "Rush to Judgment" movie was out and the assassination industry was running full-steam. Maybe the meeting took place after the assassinations of King and RFK. We don't have the context of the meeting.