FILE - In this Friday, Nov. 22, 1963 file photo, President John F. Kennedy slumps down in the back seat of the Presidential limousine as it speeds along Elm Street toward the Stemmons Freeway overpass in Dallas after being fatally shot. First lady Jacqueline Kennedy leans over the president as Secret Service agent Clint Hill pushes her back to her seat. "She's going to go flying off the back of the car," Hill thought as he tried to secure the first lady. (AP Photo/James W. "Ike" Altgens)