The Real Life Colonel Kurtz

The film Apocalypse Nowis based on the Joseph Conrad 1902 novella Heart of Darkness. Director, Francis Ford Coppola updated the Kurtz character to be a Special Forces Colonel during the Vietnam War. I've been reading about the Vietnam conflict recently, and I stumbled upon this nugget (From the Historical Dictionary of the 60's - James Stuart Olson):

RHEAULT CONTROVERSY. Colonel Robert Rheault was commander of the Fifth Special Forces Group in South Vietnam in 1969 when he was arrested for ordering the killing of a South Vietnamese Special Forces employee, whom Rheault learned was a secret agent of the Vietcong. Eventually, the case had to be dismissed because the Central Intelligence Agency (CIA) refused to release sensitive, classified documents to the prosecution. Rheault resigned from the Special Forces in 1969. REFERENCE: Charles M. Simpson III, Inside the Green Berets: The First Thirty Years, 1983.

The case received some coverage when it came out Time Magazine, 1969:

Ripples of Disbelief. The Army did nothing to lessen the mystery. The killing was said to have occurred June 20 near the Special Forces headquarters at Nha Trang, 200 miles northeast of Saigon. Rheault was relieved of his command on July 21. Who the victim was, what his connections with the war might have been, who brought the charges — all these facts remained secret. Regular military investigating units professed to have no knowledge of the incident, leading to conjecture that the case involved a secret agency, possibly the CIA. This speculation was supported by the fact that at least three of the Green Berets were intelligence specialists. According to one story, the victim was a Vietnamese spy for the Americans, who had disappeared when he was discovered to be a double agent. No body has been found, and rumor has it that the victim was disposed of at sea. Such a killing would not be unique in Viet Nam, not difficult to disguise. Why the Army chose to publicize the case is another mystery.
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Mrs. Rheault said she had sensed that something was wrong from her husband's most recent letters, but relatives of the others said that they had not been aware of any difficulties until news reports of the arrests appeared.

The assasination was of apparant double-agent Thai Khac Chuyen. It was considered excessive, and the army tried to court marshall Rheault. Nixon and Kissinger put on pressure from above and the charges were dropped.

From Apocalypse Now screen play:

WILLARD (v.o.)"October 1967 on special assignment, Con Tum province. Kurtz staged operation Arch Angel with combined local forces. Raid a major success. He received no official clearence. He just thought it up and did it. What balls. They were gonna nail his ass to the floorboards for that but after the press got hold of it they promoted him to full colonel instead. Oh man, the bullshit piled up so fast inVietnam, you needed wings to stay above it."
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WILLARD (v.o) "Kurtz's patrols in the highlands coming under frequent ambush. The camp started falling apart...November: Kurtz orders the assassination of three Vietnamese men and one woman. Two of the men were Colonels in the South Vietnamese army. Enemy activity in his old sector dropped off to nothing. Guess he must have hit the right four people. The army tried one last time to bring him back into the fold."