A masked robber rejected the money he had demanded from a Riverhead gas station attendant and struck the worker with a gun on Thursday, Riverhead Town police said.

Detectives want the public’s help in finding the suspect in the attempted robbery of Empire Gas on Old Country Road about 1:30 a.m.

The robber, who wore a dark-colored ski mask, hit the worker on the side of his face with a handgun, and without taking the money, he ran off in a southeast direction, police said.

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Patrol officers and a state police canine unit searched the area, authorities said. Police said the suspect wore dark clothing; other details on the suspect were not released.

Detectives ask anyone with information to call 631-727-4500.