SAN FRANCISCO -- Two armed gunmen sent diners at San Francisco's popular Blowfish Sushi restaurant scrambling for the floor Friday evening in an apparent robbery attempt.

SF police did not released any details of the attempted robbery, but a diner -- Greg Koch -- told KTVU he was dining at the Bryant Street restaurant with friends when he heard what he thought might be a balloon popping.

"Five seconds later there was another pop and everyone was starting to scramble and get on the floor," he said. "The people we were with saw a couple guys running across the street."

Koch continued: "Everyone was just kind of having dinner and relaxing and they came in the place and just robbed the restaurant."

He said it appeared that the cashier may have pistol-whipped.

"It's uncomfortable, you don't want to be in a situation like that," he said. "We were just here having dinner and the next thing you known, someone is shooting at you."

"It good that no one was killed," Koch continued as he stood outside the restaurant. "The girl in the back -- by the cash register -- was pistol-whipped and I think she's in the hospital."

There was no immediate word on the cashier's condition or possible suspects.