The true story is that the scum bag being summarily executed was a high level Viet Cong operative who organized and was a leader of the Tet Offensive in the City of Hue.
The Viet Cong devastated Hue and murdered a large fraction of the population.
The scum bag being executed had personally rounded up the families of dozens of South Vietnamese leaders and executed the entire families - men, women and children.
He was a terrorist caught engaging in acts of terror wearing civilian clothing and no uniform
By the Geneva Convention he was an enemy combatant caught engaged in acts of terror and war crimes in the heat of battle and subject to a lawful summary execution which he richly deserved.