A armed suspect robbed a Franklin Square Citibank on Monday, Nassau County police said.

Nassau police said the man entered the bank at 670 Franklin Ave. around 9:10 a.m. and demanded money from the teller.

The suspect, who wore a dark mask and had a handgun, got away with an undetermined amount of cash. Police said he left through a rear door, heading north toward the Franklin Gates shopping center.

The five employees and five customers in the bank at the time of the robbery were unharmed.

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The suspect is described as standing between 5 feet, 7 inches and 5 feet, 10 inches tall and was wearing a gray hooded sweatshirt, gray sweatpants and gloves.

Police ask that tipsters call Nassau County Crime Stoppers at 800-244-8477. All callers remain anonymous.