Updated

An Army soldier pleading guilty to killing a teenage girl says he shot her twice in the head only after he thought he saw "the glint of a gun" as her car door opened.

Sgt. Anthony Peden was sentenced to life in prison Thursday by a southeast Georgia judge for the December 2011 slayings of 17-year-old Tiffany York and her boyfriend, former soldier Michael Roark. Prosecutors say the couple was slain by a group of soldiers in woods near Fort Stewart to protect an anti-government militia group to which the killers belonged.

Peden will eligible for parole after 30 years, a lighter sentence than two other defendants who struck plea deals in the case. That's because evidence showed Peden struggled with brain injuries and post-traumatic stress from combat deployments.