Officers were called to the 8700 block of S. Braeswood, near Gessner, in response to a shooting call just after 9:30 p.m. Thursday.
When officers arrived at the scene, they found a man inside the taco truck who had been shot at least once. He was taken to an area hospital in critical condition.
Investigators believe the man was an employee of the taco truck.
Officers said a small, gray sedan pulled up to the taco truck and fired multiple shots before fleeing.
Nearby businesses had surveillance cameras that captured the shooting, police said.