Jim Flores, 35, was conducting a pre-inspection of his 18-wheeler at about 10:15 a.m. on the Compass Well Service yard when he walked around behind the rig, according to Live Oak County Sheriff Larry Busby.
Meanwhile, Logan Toefer, 29, of George West, was backing up and turning in his pickup.
Toefer saw Flores and went for the brakes but missed them, Busby said.
Flores complained of pain in the left chest area and his left leg.
A HALO flight transported Flores to Corpus Christi Spohn Memorial.
In addition to Live Oak County Deputy Sheriff Eric Mendoza, the George West Volunteer Fire Department and Acadian Ambulance Service responded to the accident.