Customers were head-butted and threatened by knife-wielding robbers at a Brighton off-licence.
One shopper suffered a cut to the face. Others were attacked in what police called a "gratuitous" show of violence.
The duo, wearing clown wigs and with handkerchiefs around their faces, burst into Southover Wines in Southover Street, Brighton, at 10.30pm last night.
Owner Jim Kornitzer arrived as the pair fled.
He said: "They'd head-butted one person, pushed another into a stack of beers and slapped a third. One was cut to the face.
"No one was seriously hurt but it was not the most pleasant of experiences.
"As I arrived, they were just coming out. They got away with the night's takings and helped themselves to some alcohol. Everyone was left pretty shaken.
"My staff did an excellent job by sensibly standing back and stopping the situation getting any worse."
The raiders were seen running towards a car in nearby Scotland Street.
Detective Inspector Graham Pratt said: "The offenders were completely gratuitous in assaulting the customers in this very violent robbery.
"It's very unusual that customers get injured in incidents of this sort where it is unfortunately often the staff who are the target of the attack.
"This was a very serious offence and we are following various lines of inquiry."
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