Afghan contractor Shir Ahmad was hired to provide security at an Afghanistan military base, but on Saturday—just 10 days after he was hired—he instead walked up to a group of soldiers and opened fire with an AK-47, killing two. Cpl. Donald Mickler Jr of Ohio, 29, and Pfc. Rudy Acosta of California, 19, were killed, and four others were wounded; three US soldiers responded and killed Ahmad, NBC News reports. Nine US soldiers have now been killed by rogue members of the Afghan security force in the past two months.