Iowa law enforcement are on the lookout for three men who robbed a Norfolk, Nebraska bank shortly before nine this morning and killed four bank employees and a customer.Iowa State Highway Patrol spokesman Sergeant Robert Hansen says officials from the Norfolk area sent descriptions of two potential vehicles to all Iowa law enforcement, and although a firm direction of travel hasn’t been established, Hansen says they could come to Iowa and troopers are on the lookout.Hansen says there are only so many ways across the Missouri River — Onawa, Missouri Valley and Sioux City — and those locations are being watched. Three people have been arrested in a nearby town, but police are sure yet if they’re suspects in the robbery.