Gainesville police are investigating an armed robbery at the Dollar General store at 1210 Thompson Bridge Road.Reports say a black man wearing camouflage and a ski mask entered the store around 11 a.m. and demanded money from the cashier, who handed over an unknown amount of money, said Cpl. Kevin Holbrook, Gainesville police spokesman.The armed robber then left the store on foot.“We do have officers in the area” searching for him, Holbrook said.Further details weren’t immediately available.