Houston police and Harris County Precinct 7 Constable's Office are investigating the scene.
Investigators said a driver was on the main lanes of the Beltway near Hillcroft when he was shot through the rear driver's side window.
The victim managed to continue on until Gessner, where he pulled into the parking lot of a restaurant and called for help. That's where paramedics arrived and took the man to the hospital.
His condition was not immediately known.
So far, investigators have not released a description of the suspect shooter or the car.