This is from MSNBC. A federal law enforcement official said Tuesday he had been told by other federal law enforcement officials that the two guns recovered in the shooting had had their serial numbers scraped off. The official spoke on condition of anonymity because the information had not been announced. A law enforcement official, speaking on condition of anonymity because the information had not been announced, said Cho was carrying a backpack that contained receipts for a March purchase of a Glock 9 mm pistol.