Witnesses scattered as gunshots were fired inside the restaurant, leaving police with the tough job of tracking them down and finding a motive.
Police said the victim was hanging out with friends when the shooting happened around 1pm at Taqueria Cancun on South Gessner near the Southwest Freeway.
The crime tape and swarm of police cars at the scene left frequent customers stunned.
"It's kind of shocking and amazing to see this because I work next door, and you would think with the way it's set up in there you would want to keep it peaceful," Johnathan Williams said. "I don't know what they were fighting for or arguing over."
Employees were inside when the shooting happened, along with about ten customers.
One man was struck several times in the head.
"I know the group of males that the victim was with, they all ran out. I know where they were sitting and, again, it appears they were just having some beers," HPD Homicide Sgt. C.D. Howard said.
Employees and witnesses were taken downtown to be interviewed by investigators.
Belen Reyes said she works in the kitchen and only heard noises. She didn't know it was gunfire at first, and she wasn't able to help investigators much because she did not see anything.
Police have identified the victim. His name will be released as soon as relatives are notified.
Investigators want to talk to the customers who left the restaurant after the incident. Anyone with information can call police or Crime Stoppers.