Clint Hill, the first Secret Service agent to reach the limo says Jackie was reaching for a skull fragment:
http://www.huffingtonpost.com/2012/04/05/clint-hill-memoir-book-jfk_n_1405318.html
He testified to this in front of the Warren Commission:
http://www.history-matters.com/archive/jfk/wc/wcvols/wh2/pdf/wh2_hill.pdf
(it's at the bottom of page 138)
A skull fragment was found the next day in this location.
I understand that some skeptics have a hissy-fit about it because IDIOT CT-LOONS think that a fragment proves a frontal bullet impact - which it does not. The shot clearly comes from behind, shattering the skull. When one factors in that there's a brain inside, and that the skull is covered by skin the action of the head and its fragments are not inconsistent with a shot from behind.
A skull fragment was found in what location?
Two skull fragments were found - one in Dealey Plaza to the left and forward of the limo at the time of the head shot; and the other was found on the floor of the limo.
Where's the supposed Hill fragment?
Nothing like it is seen on the back of the limo.
Here's Hill's original statement:
http://jfkassassination.net/russ/testimony/sa-hill.htm
"I jumped onto the left rear step of the Presidential automobile. Mrs. Kennedy shouted, "They've shot his head off;" then turned and raised out of her seat as if she were reaching to her right rear toward the back of the car for something that had blown out. I forced her back into her seat and placed my body above President and Mrs. Kennedy."
Here's his testimony to the Warren Commission:
"Between the time I originally grabbed the handhold and until I was up on the car, Mrs. Kennedy--the second noise that I heard had removed a portion of the President's head, and he had slumped noticeably to his left. Mrs. Kennedy had jumped up from the seat and was, it appeared to me, reaching for something coming off the right rear bumper of the car, the right rear tail, when she noticed that I was trying to climb on the car. She turned toward me and I grabbed her and put her back in the back seat, crawled up on top of the back seat and lay there."
Note that Hill never says he saw anything that Jackie was reaching for. He says in both statements her actions merely gave the appearance of her reaching for something.
My honest appraisal? He was Mrs. Kennedy's personal bodyguard - with her on many occasions. He thought very highly of her. I think he simply tried to sugarcoat it and didn't want to say anything that could embarrass her.
That's simply my opinion.
Hank