Fond du Lac police are investigating the armed robbery of a convenience store. Police say the masked robber stole an undisclosed amount of cash at knifepoint from the Kool Quick Stop on South Main Street Monday night. Police chief Aaron Goldstein says nobody was injured. The suspect’s image was captured on a store surveillance camera. The suspect is described as a white male wearing a black jacket, gray sweatshirt, and wearing a mask. He fled the scene on foot. Anyone with information is asked to call police.