NOV 22, 1963. President John F. Kennedy is shot and killed during a motorcade movement in Dallas Texas. Movies, Books, and endless television documentaries, debunk or support the Warren Commission Report. There are a lot of strange facts about the assassination. These have fed dozens of different conspiracy theories over the years. One, which cannot possible be true, blames a Secret Service agent for accidently shooting the President with an AR-15 from the automobile directly behind the presidential limousine. Presumably, this would be the third or fourth shot, depending on how many Oswald actually fired.
The lower rifle is a Carcano similar to the one used by Kennedy assassin Lee Harvey Oswald and recovered in the school book depository.
This theory, although interesting, is bunk. The firing signature of the AR-15 at that range is significantly different than the Carcano rifle Oswald used. A shot from the trailing car would have been seen and heard (as something different) by hundreds of people who witnessed the assassination.
Early model AR-15 similar to the one used by the Secret Service in Dallas
The AR-15 is one of the most wrongly vilified weapons of all time. It was used to protect the President Kennedy, not kill him.