Unconscious limo driver @

There was a black limousine at the intersection of Redwood Hwy Frontage Rd and Tiburon Blvd (131) tonight about 5:00pm.  I was behind this vehicle when the light turned green, and it did not move.  After tooting the horn, I drove around the vehicle, and the driver was slumped sideways.  I pulled over up the street, and called 911.  By the time I was communicating with the dispatcher, a sheriff had pulled up and was checking out the situation.  Does anyone know what the situation was?  All I can recall of the vehicle was a license plate frame that read:  Privately Owned.  Not for Hire.  And the driver was male, roughly 40-ish looking.  I was too far up the street to run over and speak with the sheriff...