The suspect wearing a black ski mask and gloves entered the store at 50 Mission Blvd. around 3 a.m., Sgt. Lisa Banayat said.
The suspect told the clerk he had a gun and left with cash. Video surveillance images from that robbery are not yet available, Banayat said.
It was the third robbery or attempted robbery at a 7-Eleven store in Sonoma County this month.
The 7-Eleven store on Middle Rincon Road in the Santa Rosa area was robbed around 12:30 a.m. on June 8 and the same suspect tried to rob the 7-Eleven store on Boyes Boulevard in Boyes Hot Springs about an hour earlier on June 7, the Sonoma County Sheriff's department said.
The clerk in the robbery was stabbed in the back. The suspect in the attempted robbery was not injured and the suspect left without cash.
The suspect in the two previous incidents is an Hispanic man with a shaved head, about 30-40 years old between 5 feet 2 and 5 feet 6 inches, the sheriff's department said.
He was wearing a black sleeveless T-shirt in both surveillance videos and a white jacket with black lines over the T-shirt in one of the videos.