He was a Russian adviser. All sorts of conspiracies abound. Cunningham states his opponent was really good. But Cunningham wasn't flying too well that day. Duke refused, telling Driscoll that he was on top of things.
Expert opinion is divided.
There's a big strand of thought amongst the flying community that anyone who gets a kill must have done well to get it. But there's another which says that Cunningham took enormous risks to get this kill and it could so easily have gone wrong. I incline to the idea that this was not the best of fights, Cunningham was not thinking straight, and that there were far more sensible things he should have done that day. The source of this information is said to be so sensitive that it cannot be revealed after seventeen years. Despite an intensive search of Vietnamese open literature the authors have found no reference that can be linked to a Colonel Tomb or Toon, however.