In the last 60 days Mr. Holmes had purchased four guns at local gun shops, Chief Oates said. And through the Internet, he bought more than 6,000 rounds of ammunition: more than 3,000 rounds for the assault rifle, 3,000 rounds of .40 caliber ammunition for the two Glocks, and 300 rounds for the 12-gauge shotgun. The guns were all bought legally, a federal law enforcement official said.