Lee Harvey was aiming for Jackie but missed.
Oswald was a movie buff, as proved by the fact that he was apprehended in a movie theater. Back in 1963 there was this belief that amateur film maker's with Super 8 cameras would replace Hollywood.
Oswald, as a movie lover, couldn't bear the thought of a future like this. When he went to work that day, he looked out the window to and saw his nemesis being wielded by Abraham Zapruder, and that's who he was aiming. Or rather what.