It was an elaborate suicide I tell ya.
Suicide-by-Lone-Gunman.
No, it was Jackie. She was sick of his tomcating and knew that if she left him she would lose her kids.
So she contacted the aliens in area 51 who were seriously pissed about Cuba (that was where their second base was) and they arranged for altered tapes to be given to Oswald and that is why he wrote "Kennedy must die" over and over.