The Omaha Police Department is investigating an armed robbery that happened Saturday morning.Officers responded to a report of a robbery at Rathskeller Bier Haus at 4524 Farnam St. at 8:28 a.m.OPD said employees told officers that a man wearing a white lab coat approached an employee who was taking out trash. According to police, the robber entered the business with the employee and then showed a handgun and demanded money. The robber took money and then forced employees into a walk-in cooler.This is a developing story. Anyone with information is urged to contact Omaha Crime Stoppers at 402-444-STOP, at www.omahacrimestoppers.org or on the P3 Tips mobile app.