The shooting happened Sunday night in the Dallas suburb of Garland and was captured on surveillance video, the Garland Police Department said. According to police, a man exited a white pickup truck, went inside the store and opened fire.
The man then got back into the truck and sped away, police said.
Four people were struck by gunfire, and three were pronounced dead at the scene, police said. The fourth was taken to a hospital in critical condition. Their names have not yet been released.
Police are still searching for the shooter.
The shooter was wearing a baseball hat, blue surgical mask and dark-colored athletic shorts. He was not wearing a shirt, police said.