How killed jonh f kennedy?

When the limousine had passed the depository, shots were fired at Kennedy for an estimated timespan of 6 to 24 seconds. During the shooting, the limousine is calculated to have slowed from over 13 mph (20 km/h) to 9 mph (15 km/h).

The shooting took place in front of Abraham Zapruder who was filming the President as he passed below his position. The transcript from his testimony can be read in full.

At one point, he testifies to the shock, disbelief, and then the horror of seeing the President murdered right in front of where he was standing.

Secret Service agent Clinton J. Hill was riding on the left front running board of the car immediately behind the Presidential limousine. Sometime after the shot which hit the president in the neck area, Hill jumped off and ran to overtake the limousine.
After the shot which hit the president in the head, Hill jumped onto the back of the limosine and clung to the car as it exited Dealey Plaza and sped to Parkland Memorial Hospital.

Photo by Ike Altgens taken after at least two shots had already been fired (detail).
There was hardly any reaction in the crowd to the first shot, many later saying they thought they had heard a firecracker or a car's exhaust backfire.