Omaha police are investigating a robbery at a Dollar General Thursday evening.According to Omaha Police Department, witnesses told officers a male suspect brandished a gun and demanded money at a Dollar General near 48th and L streets. The suspect fled after receiving the cash.Police said the individual was wearing all black clothing, a black hoodie and a white face mask.According to Omaha police, the suspect had a black handgun.Anyone with information about the incident can contact Crime Stoppers by calling 402-444-STOP (7867) or by going to www.omahacrimestoppers.org.