Jeff Nimrick, manager of the Macomb Farm King, was in his office at about 12:30 p.m. Wednesday shortly before Jonathan L. Labbe walked in with an AR-15 semiautomatic rifle. Labbe, 19, of Tennessee, Ill., wanted ammunition. "I want you to unlock all of the ammunition cases," said Labbe as he put the barrel of the unloaded AR-15 to Farm King employee Jon Robinson's chest.