The robbery happened at 1:14 a.m. on Oct. 23 at a 7-Eleven store in the 3100 block of Oak Road in unincorporated Contra Costa County, sheriff's spokesman Jimmy Lee said.
Two males entered the store with handguns and ordered the clerk to get down on the floor, Lee said. The men then took some cash and fled without injuring anyone.
The first suspect was described as a heavyset Hispanic or white male wearing a black hoodie, white T-shirt and dark blue or gray pants.
The second suspect was described as a Hispanic or white male wearing a black jacket with a logo on the front and gray pants.
Both suspects have their heads and faces covered in the surveillance photos.
Detectives believe that the same two suspects might have robbed the same store before, Lee said. The sheriff's office hopes that the release of the photos will help them identify the suspects.
Both men should be considered armed and dangerous. Anyone with information about their identities is asked to call the sheriff's office at (925) 313-2653.