The Army’s Criminal Investigation Command has reopened its investigation of an Afghanistan war hero who Army officials said confessed to killing an unarmed Taliban detainee.

The service is again scrutinizing former Maj. Mathew L. Golsteyn after he appeared in a Fox News television interview in October and acknowledged that he had killed a Taliban bombmaker who had been held as a detainee during the bloody battle of Marja in February 2010. The suspected bombmaker was not on a list of targets that U.S. forces had been cleared to kill, according to Army documents; Golsteyn said that letting go of the insurgent meant the Taliban member could later target Afghans who are helping U.S. troops.

“You realize quickly that you make things worse,” Golsteyn said in the interview. “It is an inevitable outcome that people who are cooperating with coalition forces, when identified, will suffer some terrible torture or be killed.”

Golsteyn first acknowledged killing the man during a polygraph test while he was interviewing for a job with the CIA in 2011. A lengthy military probe followed. Army documents obtained through the Freedom of Information Act last year show that the service investigated Golsteyn on charges of murder and conspiracy but closed the case after determining that it did not have any evidence to prosecute. The results of his polygraph would not be admissible in court, defense officials said.

Lt. Col. Jennifer Johnson, an Army spokeswoman, said in a statement that it would be “inappropriate to comment further regarding an ongoing investigation.” A spokesman for Army Criminal Investigation Command, Christopher Grey, declined to comment.

Golsteyn said Thursday in an email to The Washington Post that he was “frustrated, but not terribly surprised” that the Army reopened its investigation into his actions. He declined to discuss what happened the day the suspected bombmaker died, but said the Defense Department and Army has “viciously pursued me without a discernible cause or a stated goal for over five years.”

Golsteyn led a team from 3rd Special Forces Group, of Fort Bragg, N.C., that had a unit of Marines deployed alongside it during the bloody Battle of Marja in February 2010. Two Marines under his command — Sgt. Jeremy R. McQueary, 27, and Lance Cpl. Larry M. Johnson, 19 — were killed and three more were wounded Feb. 18 after a metal sliding door booby-trapped with explosives detonated.

Two days later, Golsteyn watched a Taliban marksman nearly hit another Marine who was manning a rooftop observation post on their base. He launched an 80-man mission to hunt the shooter down, slogging through a muddy field under fire to help a wounded Afghan soldier, returning fire with an antitank weapon, and coordinating repeated airstrikes by F/A-18 Hornet fighter jets and a Predator drone. He was awarded a Silver Star, the military’s third-highest award for combat valor, and service officials later recommended an upgrade to the more prestigious Distinguished Service Cross.

Army documents show that Golsteyn’s unit launched a search for bombmaking supplies in the area after the deaths of Johnson and McQueary, and detained the man Golsteyn confessed to killing. A tribal leader working with the Americans identified the detainee as a member of the Taliban but worried the detainee knew who had singled him out. The tribal leader’s immediate fear: If Golsteyn’s unit let the detainee go, he would kill him and his family.

Golsteyn told the CIA during his polygraph test that he trusted the tribal leader and “had no qualms” about killing the bombmaker “because he couldn’t have lived with himself if [the suspected bombmaker] killed another Soldier or Marine,” Army documents said. During Golestyn’s interview with the CIA, according to Army investigators, he described taking the bombmaker off the base, shooting him and burying his remains in a shallow grave. Golsteyn added that later that night, he and two other soldiers dug up the remains, brought them back to their base and burned them in a pit used to dispose of trash.

Golsteyn and his attorneys have long maintained that the Army’s characterization of events is filled with exaggerations and leaps of logic. No other service members would serve as witnesses against Golsteyn, even when investigators offered immunity from prosecution. Then-Army Secretary John M. McHugh stripped Golsteyn of his valor award in fall 2014, and the Army also revoked his Special Forces tab and reassigned him as a conventional infantry soldier.

Golsteyn said in his email to The Post that his case was reopened despite an Army administrative board determining last year that the murder accusation against him was unfounded. The panel did find that Golsteyn demonstrated conduct unbecoming an officer and recommended a general discharge under honorable conditions, ensuring he could keep health benefits.

Senior defense officials, Golsteyn said, continue to talk tough about the fight against the Islamic State group while they “mischaracterize my combat actions as ‘murder.'” He compared his case to that of another officer, former 1st Lt. Clint Lorance, who was convicted of second-degree murder in 2013 for ordering his soldiers to open fire on village elders in Afghanistan who were approaching his unit while they were on patrol. Several member of Lorance’s platoon testified against him after being offered immunity.

“I am filled with moral disgust that such individuals can continue to wreak such havoc on our warfighters without consequence,” Golsteyn said, adding that he does not regret doing the TV interview because it was important to speak out on how soldiers are restricted in combat.

Rep. Duncan D. Hunter (R.-Calif.), a member of the House Armed Services Committee who has clashed with the Army repeatedly about Golsteyn’s treatment, said Thursday that he was disgusted with the Army’s decision to reopen the case. Gen. Mark A. Milley, the Army’s top officer, and Army Secretary Eric Fanning told Hunter that they cannot stop the investigation at this point, Hunter said.

“Matt Golsteyn is an American hero. Matt Golsteyn does for the American people what we ask him to do, and the Army is screwing him again,” Hunter said. “I’m embarrassed for the U.S. Army — and they ought to be embarrassed.”

In a letter sent Wednesday to Milley and Fanning, Hunter wrote that they have “the ability to fix this stupidity.”

A senior Army official, speaking on the condition of anonymity because of the sensitivity of the case, said a request for information on the Army’s handling of the case has been filed with the Defense Department Inspector General. Until that is resolved, the official said, the case is on hold.