The May 1964 reenactment, conducted by the FBI with assistance from the Secret Service, was an effort to understand exactly how the shooting occurred. Of primary concern was learning how three bullets accounted for the known wounds to President Kennedy and Governor Connally. An FBI summary prepared early in December 1963 concluded the first shot hit Kennedy in the upper back, the second hit Connally in the back, and the third hit Kennedy in the back of his head.
Kennedy's limousine, rebuilt right after the assassination and put back in service for President Johnson, was not available for the reenactment. So the FBI used the Secret Service follow-up car that had been driven by Secret Service agents right behind Kennedy.
By using the Abraham Zapruder, Orville Nix and Marie Muchmore films of the assassination and by rolling the car down Elm Street to correspond to the frame-by-frame movements in those films, investigators measured angles and distances from the rifle to the target and other Dealey Plaza landmarks. Months later, investigators used that information to include information that a bystander had also been slightly wounded during the assassination.
Eventually, the Warren Commission concluded the first shot probably missed, the second hit Kennedy and also Connally, and the third struck Kennedy in the head. The "Single Bullet Theory" - which refers to the trajectory of the second bullet - remains one of the most controversial aspects of the assassination. - Gary Mack, Curator