I was 9 years old when Kennedy was assasinated, I remember the day clearly.
I tend to believe there was more than one person involved. I do believe the bullet that hit Kennedy in the back came from Oswald. But I have seen the films dozens of times and that last bullet did not seem to come from the rear.
I saw a show quite a few years ago where a fellow did extensive research, and he believed there was a gunman at street level in a storm drain. He showed how a man with a rifle could stand in this drain and make the last shot. It lined up perfect. He also showed how this gunman could quickly walk underground in the sewer system and come out at a creek several blocks away. I was very impressed because they simulated the car coming down the street and showed with photography that a gunman could have easily hit Kennedy on the front right side of his head from this drain.
I was always very skeptical that Oswald acted alone. It was just too easy when he was killed in the Dallas Police Station. Ruby got past all security and just walked right up to Oswald. Too easy.
I also saw an interview with one of the doctors who tried to save Oswald. He said he received a call from LBJ who demanded an autopsy in the morning. He told the President that Oswald was in bad shape, but he was still alive and they were doing everything they could to save him. Again, LBJ repeated that he expected an autopsy on his desk in the morning.
The reporter asked this doctor what impression he got from this, and he said he got the impression that LBJ wanted Oswald dead.
So, we will never know the answer. Who knows, perhaps Oswald just got lucky and hit his target.