Marshalltown police are trying to track down a bank robber. Police Chief Lon Walker says a lone robber struck around opening time on Tuesday. The Chief says at a little after nine a.m., a white man wearing a baseball cap, Kansas City Chiefs jersey and bluejeans went into the F&M Bank on First Avenue in Marshalltown. He demanded money and told the teller he had a gun under his shirt, then fled out the bank’s west door. The chief says he’s frustrated not to have found a lead on the robber. There were police officers on-site within just a few minutes, three cars at the bank and others within minutes doing a general search of the area, but nothing’s turned up.