Police are scratching their heads trying to work out who donated a human skull to a thrift store in Austin, Texas. A homicide detective says that foul play is not suspected and that he just wants to know how the adult skull came to be left at the Goodwill store. Staff discovered it while sifting through donations last month. A rep says it could have been donated up to a week prior to its discovery. No other details about it have been released. This is at least the fourth skull to be donated to the international nonprofit this summer. Three were donated in July to a Goodwill store in Bellevue, Wash.