The man walked into the Heng-Heng store in the 1000-block of West Argyle at about 2:35 p.m. pretending to be a customer, police said.
He tried to leave the store without paying for the jewelry he was handed and when the door wouldn't open, police said he took out a gun, shot the glass out and took off.
The door would not open because the customers need to be buzzed out.
No injuries were reported, police said. No one is in custody and Area Three detectives are investigating.
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