Here's the "official" update:
http://xml.sun-sentinel.com/news/local/palmbeach/sfl-1226manincanal,0,7234615.story
They say the then 42 year-old man, who was taking a prescription pain medication for his back, went off the road by accident because there was no sign of foul play. He was apparently seatbelted in the car.
I don't believe it because:
1. Palm Beach police are on a par with Beverly Hills Cops and Reno 911, and
2. Take a look at the map. The "20000 block" of Lox road is just the Everglades. Who takes their hot SL on a joyride there
, especially without anyone else knowing?