While it is possible Oswald worked with another gunman, there is no reason for him to do that. Everything done is something anyone with basic gun knowledge could have done alone.

As I said elsewhere, the only evidence of a second gunman is we know Oswald was a good shot with a gun and so needing 3 shots (with a scoped rifle at close range - less than 100 meters) is something to question. But in the end it seems more likely he would have pulled the trigger himself and thus not needed help.