Choi had also been working at the currency exchange when it was held up by three men July 27 at about 11:30 a.m. That case is still open as well.
"Brian was a good man, devoted husband and father and respected member of the Community Currency Exchange Association," said John Iberl, President of CCEA.
The Community Currency Exchange Association of Illinois is offering the $10,000 reward.
Anyone with information should contact the Chicago Police Department, Area 5 Detective Division at 312-746-8282.
The Sun-Times Media Wire contributed to this report.