"I think that he was on drugs because he looked like he was nervous but he was so excited like a weird guy," said Georgina Ruiz who was working at the time of the robbery.
Police said the suspect fled with $120 and a new cell phone.
"Highly dangerous guy to go into a business that's open with people inside with a handgun and rob the place in broad daylight," said deputy Mark Pope of the L.A. County Sheriff's Department. "We're asking everyone to take extreme caution if they do recognize him committing a crime in the future."
In the four weeks since the robbery store owners said they have up graded their surveillance system from a total of two cameras to 15.
Detectives believe the same man may be responsible for another armed robbery three days later at a discount store about a mile away. The suspect made off with about $200 in cash the second robbery.
Anyone with information is urged to call the Century Sheriff's Station at (323) 568-4909.