Secret Service Agent William Greer was driving President Kennedy, the First Lady, Texas Governor John Connally and the Governor's wife Nellie on their trip through Dallas. Greer was an Irish immigrant to the United States who had worked for the Secret Service since October 1 1945 (see his testimony to the Warren Commission here). He had risen up the order of seniority, driving back up cars, sometimes chauffeuring for President Eisenhower and, more often, for Mrs Eisenhower. He became the main chauffeur for the President upon the inauguration of President Kennedy.
Now for some reason people seem to see in the videos of the assassination something sinister in the driver turning around after the first shot. See this popular Youtube video.
This assassination is a hotbed of discussion and armchair detective work. Unfortunately in the fever to provide something "new", people are willing (on the flimsiest evidence) to accuse the most innocent of people of murder.
I'm afraid as we move into the more meatier and popular theories we shall see this on an even larger scale. Alas.
Stephen King's 11.22.63 - Amazon.com, Amazon.co.uk
Four Days in November: The Assassination of President John F. Kennedy - Vincent Bugliosi - Amazon.com, Amazon.co.uk
Crossfire: The Plot That Killed Kennedy - Jim Marrs - Amazon.com, Amazon.co.uk