A Japanese woman has been arrested in connection with the fatal stabbing of a U.S. airman stationed at the Yokota Air Base in western Tokyo. Air Force officials on Saturday identified the service member as Master Sgt. Nicholas Vollweiler, 35, a native of Pennsylvania assigned to the 374th Security Forces Squadron. Vollweiler died Friday after he was stabbed with a knife outside his home just outside the air base. A 27-year-old Japanese woman identified as Aria Saito in local media reports was arrested at the scene of the stabbing. She initially faced attempted murder charges but Tokyo police have now reportedly upgraded the charge to murder. No further details were available on a motive.