. >> as the three agents made their way eastward towards yosemite, deputy sheriff rod sinclair of the mariposa county sheriff's office was preparing to check the road closings for the queen's visit. >> rod was a big man, heavy, and was quite macho and authoritative. >> we had heard, but we never deduced hard evidence of this fact, that sinclair was something of a loose cannon. >> sinclair and another deputy climbed into a chevy impala patrol car, similar to this one, and sped west on highway 132 to check on the road closings. at the same moment, the secret service agents continued eastward in a small rental car. none of the agents was wearing a seatbelt. the road was wet from a light rain. both sinclair and the convoy of secret service agents believe the road had been cleared of traffic. >> the sheriff's car was coming from our right, around this curve. the secret service cars were coming from our left. >> the road curved around the small hill that blocked the driver's view of approaching cars. that location had been the scene of seven accidents in the previous three years. at 10:31 a