Former 1st Lt. Michael Behenna of Edmond had served five years of a 15-year sentence for his 2009 conviction on a charge of unpremeditated murder in a combat zone.
Behenna's mother, Vicki Behenna, an assistant federal prosecutor in Oklahoma City, said she "immediately started crying" after learning about her son's release.
"He called me today (Wednesday), actually on my way into work at about a quarter 'til 9," Vicki Behenna said. She said he was scheduled to be released on March 14.
The Army Clemency and Parole Board denied Behenna's request for clemency but granted him parole, Col. David Patterson said. He said the decision was based on factors "including a strong parole plan with family and community support."
Vicki Behenna, of Edmond, said her son would work on a southwest Oklahoma cattle ranch and take classes at Oklahoma State University.
"He thinks he wants to begin ranching, to raise cattle," she said.
Efforts to contact Michael Behenna, 30, at Fort Leavenworth, Kan., where he was being held, were unsuccessful.
"He's not been allowed to talk to the media at all," his mother said.
There was no dispute that Behenna was supposed to take the Iraqi prisoner home, but instead took him to a secluded railroad culvert, stripped him naked and shot him twice after interrogating him at gunpoint about an April 2008 roadside bombing that killed two men under Behenna's command.
Behenna said he acted in self-defense when the man reached for Behenna's handgun. The Army argued he could not claim self-defense because he was conducting an unauthorized interrogation at gunpoint.
Behenna's family had fought to overturn the conviction, but the U.S. Court of Appeals for the Armed Forces and the U.S. Supreme Court upheld the decision.
Behenna drew support from Oklahoma Gov. Mary Fallin and the state's congressional delegation following his conviction.
"I am glad this long ordeal has finally come to an end for Michael Behenna and his family. Michael went to Iraq to serve his nation and to defend liberty both here and abroad. Instead, he found himself mourning the loss of his friends from the inside of a cell," Fallin said in a statement Wednesday.
"I believe the Army acted appropriately and compassionately in offering him parole."
Sen. Jim Inhofe and Reps. James Lankford, Tom Cole, Frank Lucas, Markwayne Mullen and Jim Bridenstine, all Republicans, also issued a joint statement praising the decision to parole Behenna.