(CBS News) DALLAS When the shots were fired in Dallas 50 years ago, only one Secret Service agent managed to reach President John F. Kennedy. Clint Hill is 81 now, but his memories are sharp. He was assigned to protect Mrs. Kennedy.
Hill was standing closest to the first lady on the side of the car following the presidential limousine.
SCOTT PELLEY: As you're beginning the motorcade through downtown Dallas, what is the crowd like and what are your concerns, if any?
CLINT HILL: Well, the crowd had really grown. It was very large. They couldn't be contained on a sidewalk. They were 15 to 20 deep on each side of the street.
SCOTT PELLEY: What are you watching as the cars go through those crowds?
CLINT HILL: Anybody that's out of the ordinary, that stands out, that isn't dressed like everybody else, that just appears different. Those are the kinds of things we have to make note of.
SCOTT PELLEY: As the motorcade turns onto Dealey Plaza what are you seeing?
CLINT HILL: Immediately in front of us was the Texas Schoolbook Depository. … We didn't see anything unusual at all … and then when we just started to straighten out and started to gain up little bit more speed was when I heard an explosive noise over my right shoulder.
The four agents on the follow-up car snapped their heads toward the noise. The two on the right side, assigned to cover the president, now looked away from the limousine. But as Hill turned, his view crossed the president's car.
CLINT HILL: I saw the president grab at his throat and move to his left, and I knew something was wrong. And so that's when I jumped from my position and began … to try and get up on the top of the back of it to form a shield there behind President and Mrs. Kennedy so no further damage could be done.
Secret Service Agent Clinton Hill hangs on to the limousine carrying first lady Jacqueline Kennedy and the mortally-wounded president, in Dallas, November 22, 1963. Hill jumped onto the back of the car as Mrs. Kennedy tried climbing out, after her husband was struck by rifle fire.
SCOTT PELLEY: Walk me through it -- your foot hits the pavement and what happens?
CLINT HILL: Well, I jumped off to my left. There was a motorcycle officer immediately to my left. So I had to get between the motorcycle and the-- and the follow-up car to get to the president's car. The two cars were separated by about five to seven feet. … And so I ran as fast as I could. … Later they told me there was a second shot while I was running. I hadn't heard it. And then just as I approached the president's car, there was a third shot. It hit the president in the head.
SCOTT PELLEY: What did you see?
CLINT HILL: Brain matter, blood, bone fragments all come out of the wound … Then Mrs. Kennedy came up on the trunk. She was trying to grab some of that material and pull it back with her. … I got a hold of her and I put her in the backseat. … And when I did that, his body fell to its left into her lap. His face-- his head was in her lap. The right side of his face was up. I could see his eyes were fixed. I could see an area through the skull that there was no brain matter in that area at all. So I assumed it was a fatal wound. I turned and gave a thumbs-down to the follow-up car crew. Wanted to make sure they knew. And then I screamed at the driver to get us to a hospital.
SCOTT PELLEY: Thumbs down meant what?
CLINT HILL: That it was-- very grave situation. I assumed it was fatal and that's what I really meant.
SCOTT PELLEY: Did you attempt to speak to the president?
CLINT HILL: No, I didn't try to talk to him at all. And Mrs. Kennedy-- she only said a couple things when I was there. She said, "Oh, I have his brains in my hand." And, "Oh Jack, oh Jack, what have they done? I love you, Jack." That's all I heard her say. There was nothing else said in the car at all.
The limo then sped on to Parkland Hospital. That is where we pick up the story with Clint Hill on Friday, when the "CBS Evening News" will be broadcasting from Dealey Plaza in Dallas to mark the 50th anniversary of the assassination.