The shooting happened at about 9:17 a.m. in the 300-block of E. 47th Street, police said.
CPD said a man walked into the store and demanded money from the register and then shot a 42-year-old man.
Police said the victim was behind the counter when he was shot.
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It was not clear if he is an employee.
The victim was shot in the arm and taken to an area hospital where he is expected to be OK.
Nobody is in custody.
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No other information was available.