What did SS agent Roy Kellerman mean when he testified that a flurry of shells came into Kennedy's limousine?
Mr. SPECTER. As you are positioning yourself in the witness chair, your right hand is up with the finger at the ear level as if clutching from the right of the head; would that be an accurate description of the position you pictured there?
Mr. KELLERMAN. Yes. Good. There was enough for me to verify that the man was hit. So, in the same motion I come right back and grabbed the speaker and said to the driver, "Let's get out of here; we are hit," and grabbed the mike and I said, "Lawson, this is Kellerman,"--this is Lawson, who is in the front car. "We are hit; get us to the hospital immediately." Now, in the seconds that I talked just now, a flurry of shells come into the car. I then looked back and this time Mr. Hill, who was riding on the left front bumper of our followup car, was on the back trunk of that car; the President was sideways down into. the back seat.
Mr. SPECTER. Indicating on his left side.
Mr. KELLERMAN. Right; just like I am here.
Mr. SPECTER. You mean, correct, left side?
Mr. KELLERMAN. Correct; yes, sir. Governor Connally by that time is lying flat backwards into her lap-- Mrs. Connally--and she was lying flat over him.
LATER in his testimony he referred to a flurry of shots...
Mr. SPECTER. Now, did President Kennedy say anything beside, "My God, I am hit."
Mr. KELLERMAN. That is the last words he said, sir.
Mr. SPECTER. Did Mrs. Kennedy say anything at that specific time?
Mr. KELLERMAN. Mr. Specter, there was an awful lot of confusion in that back seat. She did a lot of talking which I can't recall all the phrases.
Mr. SPECTER. Well, pinpoint--
Mr. KELLERMAN. But after the flurry of shots, I recall her saying, "What are they doing to you?" Now again, of course, my comparison of the voice of her speech--certainly, I have heard it many times, and in the car there was conversation she was carrying on through shock, I am sure.
Is this evidence of a conspiracy??
It is possible to pinpoint, very precisely, when the "flurry" occurs by just following Kellerman's testimony.
Kellerman looks in the back of the limo and sees that JFK is hit.
He turned back, facing forward, grabbed the in-car mic and shouted at Greer to step on it.
He called into the mic "Lawson, this is Kellerman. We are hit; get us to the hospital immediately."
While he is telling Greer to move it and talking to Lawson the "flurry of shells" comes into the limo.
When we examine the clip below the "flurry of shells" appears to be related to the head shot.
Kellerman turns to look back into the limo.
It must be at this time he sees that JFK is hit.
He instantly turns back and we must assume it is at this moment he is telling Greer to go and talking into the mic.
As this is happening the head shot occurs.
The thing to notice is that both Kellerman and Greer duck down in the limo.
This must surely be a response to the "flurry of shells" coming into the limo at exactly the same time the head shot.

The flurry of shells is connected to the head shot.
It is explained by the bullet that hit JFK's head fragmenting. A number of these fragments peppered the inside of the front of the limo, cracking the windshield and denting the chrome trim.