An Army soldier has pleaded guilty in a southeast Georgia courtroom to shooting a former military colleague to protect an anti-government militia group.

Pvt. Christopher Salmon pleaded guilty to malice murder charges Thursday and was sentenced to life in prison with no chance of parole.

Salmon testified that he shot Michael Roark twice in the head while another militia member killed Roark's girlfriend, 17-year-old Tiffany York.

Salmon turned to face Roark's parents in the courtroom and said, "I'm sorry I killed your son."

Salmon says he and other disgruntled Fort Stewart soldiers formed a militia group that stockpiled weapons and plotted killings. He says Roark and York were killed because group members feared they planned to expose the organization to police.