On September 14, 1924, Patrol Inspector James F. Mankin was killed by the accidental discharge of a Service rifle. The accident occurred about 18 miles northeast of Laredo near the Rio Grande River where Patrol Inspector Mankin, along with Patrol Inspectors Buck West and Ralph R. Dockum, were patrolling in a government vehicle. The officers, upon reaching the banks of the river, alighted from the car to determine whether or not any crossings had been made. There were two rifles in scabbards in the back of the car along with camping gear and other articles. The two officers were rearranging the items in the back of the car when a .30 caliber government rifle slipped out of the car, the hammer striking the running board and discharging the gun. The bullet struck the back of the front seat where the bullet split, one part to the left striking Dockum’s face and the other to the right striking Inspector Mankin behind the right ear. Inspector Mankin died less than thirty minutes after the accident.