Former Smithville city policeman Nathan Estes, 38, lost his life in a one-vehicle accident in Smith County Tuesday morning.According to the THP, Estes was traveling north on State Route 164 near Temperance Hall just before 7 a.m. when his 2000 Chevrolet pickup left the roadway on the left side and struck a tree. The truck reportedly went into a skid and overturned, ejecting Estes from the vehicle.The truck apparently came to rest against another tree with Estes partially pinned underneath the vehicle. Authorities said he was not wearing a seatbelt.The accident was investigated by Gerald Carter, Tommy Cooper and Eric McCormick of the THP.