SIOUX FALLS, S.D. (KELO AM) - Police say a 38-year-old Sioux Falls man was assaulted by a suspect armed with a bat last night as he was entering the HyVee Store on West 26th Street and Marion Road.     Officer Sam Clemens says the victim told investigators that he was about 20 feet from the entrance when he was hit in the back of the head.     Clemens says a witness saw four men walk up to the victim and one hit him with the bat.  She says they all ran after the attack and she could not provide descriptions.     Clemens says the victim doesn't know the assailants or why they would attack him.     He was treated for a cut to his head and checked for any signs of a concussion.