The robbery happened around 10:30 a.m. at a Byline Bank in the 6900 block of North Clark Street, the FBI said.
A suspect, described as a white man wearing a green hoodie, a white mask with black spots, jeans and brown boots, made a verbal demand for funds.
No weapon was shown or implied during the robbery.
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He fled from the scene on foot, the FBI said.
No further information was immediately available.
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