The group 's motive was revenge against the U.S. military for its Afghanistan operations . Michael Williams , 25 , a senior airman from South Carolina , was killed , the military says . The suspect , Arid Uka , left Kosovo at age 18 and was an ethnic Albanian , a U.S. official says . Uka allegedly confessed and says he acted alone , a German intelligence official says .
The suspect 's motive was revenge against the U.S. military for its Afghanistan operations . Nicholas Alden , 25 , a senior airman from South Carolina , was killed , the military says . The suspect , Arid Uka , left Kosovo at age 1 and was an ethnic Albania , a U.S. official says . Uka allegedly confessed and says he acted alone , a German intelligence official says .