San Diego ? A man in his 70s has robbed a bank branch inside a San Diego supermarket.

Police investigators say the man handed a teller a note demanding cash Friday at the U.S. Bank inside a Vons supermarket in the Carmel Valley neighborhood. The man said he had a gun, but no weapon was seen.

He escaped with an undisclosed amount of cash.

Investigators say the suspect may be responsible for similar robberies at banks in La Jolla and Santee in August and September. In one robbery, a suspect with a similar description was carrying an oxygen tank.