It happened around 6:45am at a Valero store in the 8100 block of Martin Luther King Jr. Blvd. at Belarbor St.
"They just came in shooting," said Ofc. T. Triplett with the Houston Police Department's robbery division.
Surveillance video from inside the gas station is shocking. At 6:30am Saturday, two clerks were tending to a customer when a masked gunman opened fire.
"The guy fired several rounds inside the store," Triplett said.
A second suspect crawled over the counter, searching for money.
"It wasn't until after the first shots were fired that any demand for money was made," Triplett explained.
Meanwhile, one of the clerks grabbed his pistol and, shielding himself, returned fire.
In all, police say at least seven rounds flew inside the store.
The suspect in the black shirt -- identified by police as Harold Odell Robertson -- was hit twice in the arm. One of the clerks was shot once in the leg.
"I think he's brave, and he knows how to shoot I guess," store owner Lion Boulos said of his employee.
After the shooting, the suspects took off. They ended up in Anthony Kilpatrick's lawn.
"I didn't know they robbed the Valero. They had said that somebody robbed them for their car," Kilpatrick said.
Leaving a trail of blood, the suspects stashed a key piece of evidence that was later discovered by Gerald Kilpatrick.
"The gun was stashed on the side of the house in some thorn bushes," he said. "[It was] face down with the handle sticking up."
Police recovered the gun. Robertson, who collapsed on the porch, was picked up by an ambulance and taken to Ben Taub General Hospital where he was recovering Saturday night.
The injured clerk was also taken to a hospital and is expected to recover.
"They had a certain intention on what they wanted to get done, and their plan failed this morning," Triplett said.
Police say the suspects may have gotten away with a small amount of cash.
So far, police are charging Robertson with aggravated robbery.
The wounded suspect's accomplice ran away, but police say they have a partial name and say they're closing in on where to find him.