Three commanders were circling overhead in helicopters. Maj. Gen. Koster was at 2,000 feet, Colonel Henderson was at 1,500 feet, and Lieut. Col. Barker was in his observation and command position at 1,000 feet. Thompson’s radio transmissions broke into the commanders’ silence about the atrocity happening below them. Shortly after, the captain on the ground got the order to stop the killing. The killing stopped, and the cover-up began.
An enraged Thompson made a full report to Colonel Henderson, but U.S. Army officers managed to conceal the massacre at My Lai for 18 months. By then, most of the enlisted men who were involved in the events at My Lai had already left military service. A year later, after an intensive investigation, the Army convened court martials for 26 men. The charges included rape, murder, and assault to commit murder. In the end, Lieutenant Calley, the lowest ranking officer on the ground at My Lai, was found guilty of the murder of 22 Vietnamese civilians. He was the only one convicted.
Calley was sentenced to life imprisonment, which was then reduced to 20 years. He served three and a half years under house arrest at a military fort, which included three months in a disciplinary barracks, and then was released on parole six years after the massacre.
Fourteen officers were charged with suppressing information related to the massacre. Most charges were later dropped. Brigade commander Colonel Henderson was the only high-ranking commanding officer who stood trial on charges relating to the cover up of the My Lai massacre. He was acquitted.