( CNN ) -- The sentencing phase begins Monday for Army Staff Sgt . Robert Bales who has admitted to gunning down 16 civilians in a 2012 rampage through two villages near his outpost in southern Afghanistan . Bales pleaded guilty in June to more than 30 criminal charges , including 16 premeditated murder counts , in a hearing before a military judge . The guilty plea spares the 39-year-old Bales the prospect of a death sentence in the killings . He now faces life in prison , but a jury of four officers and two enlisted personnel will decide whether he will have a chance at parole . Bales admitted to slipping away from his outpost in southern Afghanistan and going on a house-to-house killing spree in two nearby villages in March 2012 , a massacre that further strained ties between American troops and their Afghan allies . But he has not offered an explanation for his actions . In addition to the murder counts , Bales pleaded guilty to six counts of attempted murder , seven of assault and the use of illicit steroids and alcohol , but pleaded not guilty to a charge of obstruction of justice . Bales is a member of the Army 's 3rd Stryker Brigade Combat Team , an element of the 2nd Infantry Division . His attorneys have said the service made a mistake in assigning Bales to another combat tour despite evidence of post-traumatic stress disorder and a traumatic brain injury suffered during a combat tour in Iraq . CNN 's Barbara Starr and Devon Sayers contributed to this report .
He admitted to shooting Afghans and killed several more in a house - to - house rampage . Bales now faces life in prison . He will decide if he will have a chance at parole .