Senator Sherman's car had just pulled onto the long suspension bridge when it went wildly out of control.  The car careened across the divider and slammed into oncoming traffic.  The bulletproof windows were up and the doors locked.  Inside was the senator...dead.  Shot once through the head.  No gun was found in the car.

Who killed the senator?  What was the motive and how could he have been shot in a locked car?