George Hickey, a secret service agent shot JFK "accidentally." Lee Harvey Oswald shot the first 2 shots that day. The first ricocheted off a traffic light. The second sliced through JFK, that's why you see his arms go up during the film. After the first shot was fired the gov'ner turned around and was hit with the same bullet that sliced through Kennedy. Then George Hickey, in possession of an assault rifle (AR-14), locates Oswald then takes off the safety and hits JFK the head.
It's already been proven with eye witness and ballistics tests.