Oswald was charged with the assassination of Kennedy, but he denied responsibility for the killing, claiming that he was a "patsy" and two days later, he was fatally shot by local nightclub owner Jack Ruby on live television.
This contradict the theory that Oswald had been the lone gunman.
How? Are you aware of who Jack Ruby was? Read Vincent Bugliosi's Reclaiming History. It goes deep into this and everything his family and friends said about him. He was a deranged man who loved Kennedy so much that people who knew him were not the least bit surprised he did what he did.
https://www.amazon.com/Reclaiming-History-Assassination-President-Kennedy/dp/0393045250