Bales, a four-tour combat veteran, will also
face other charges, including attempted murder, but the official was unable to say how many additional counts there would be.
Legal proceedings would likely take place at Bales' home base, Joint Base Lewis-McChord, close to Tacoma, Washington, the U.S. official said.
Bales, 38, is being held in solitary confinement at a military detention center in Leavenworth, Kansas.