After evacuating a child to a Quảng Ngãi hospital, Thompson angrily reported to his superiors at Task Force Barker headquarters that a massacre was occurring at Sơn Mỹ.

Immediately following Thompson's report, Lieutenant Colonel Frank A. Barker ordered all ground units in Sơn Mỹ to cease search and destroy operations in the village.

Thompson was condemned and ostracized by many individuals in the United States military and government, as well as the public, for his role in the investigations and trials concerning the Mỹ Lai massacre.

[1] Despite the adversity he faced, he remained in the Army until November 1, 1983, then continued to make a living as a helicopter pilot in the Southeastern United States.

[4]: 47  In 1964, Thompson received an honorable discharge from the Navy and returned to Stone Mountain to live a quiet life and raise a family with his wife.

[4]: 59 Army intelligence concerning the presence of Viet Cong in Sơn Mỹ was inaccurate, however, and the village's population was predominately composed of neutral, unarmed rice-farming families.

Reconnaissance aircraft, including Thompson's OH-23 crew, flew over the Sơn Mỹ vicinity but received no enemy fire.

Upon entering Sơn Mỹ, officers and soldiers of Company C moved through the Song My Village and vicinity, murdering civilians, raping women, and setting fire to huts.

[4]: 69 [6]: 137 [9] 1st Platoon of Company C, commanded by Lieutenant William Calley, forced approximately 70–80 villagers, mostly women and children, into an irrigation ditch and murdered the civilians with knives, bayonets, grenades, and small arms fire.

[4]: 73 Thompson recounted at an academic conference on Mỹ Lai held at Tulane University in December, 1994: "We kept flying back and forth, reconning in front and in the rear, and it didn't take very long until we started noticing the large number of bodies everywhere.

"[10] Thompson and his crew, who at first thought the artillery bombardment caused all the civilian deaths on the ground, became aware that Americans were murdering the villagers after a wounded civilian woman they requested medical evacuation for, Nguyễn Thị Tẩu (chín Tẩu), was murdered right in front of them by Captain Medina, the commanding officer of the operation.

Thompson then radioed a message to accompanying gunships and Task Force Barker headquarters, "It looks to me like there's an awful lot of unnecessary killing going on down there.

According to Trent Angers in The Forgotten Hero of My Lai: The Hugh Thompson Story (2014), The helicopter looped around then set down quickly near the edge of the ditch.

[4]: 215 [12][13] After transporting the child to the hospital, Thompson flew to the Task Force Barker headquarters (Landing Zone Dottie), and angrily reported the massacre to his superiors.

The citation for the award fabricated events, for example praising Thompson for taking to a hospital a Vietnamese child "...caught in intense crossfire".

[4]: 146  In the last incident, his helicopter was brought down by enemy machine-gun fire, and he broke his back in the resulting crash landing.

There, he was sharply criticized by congressmen, in particular Chairman Mendel Rivers (D-S.C.), who were anxious to play down allegations of a massacre by American troops.

[6]: 290–291  Rivers publicly stated that he felt Thompson was the only soldier at Mỹ Lai who should be punished (for turning his weapons on fellow American troops) and unsuccessfully attempted to have him court-martialed.

"[16][7] After his Vietnam service, Thompson was assigned to Fort Rucker to become an instructor pilot and later received a direct commission, attaining the rank of captain and retired as a major.

In 1988 an English documentary film producer, Michael Bilton, working for Yorkshire Television, managed to contact Thompson via his mother, who was then widowed and living in Texas.

The interview showed Thompson relating what he had witnessed at Mỹ Lai: "Here we were supposed to be the guys in the white hats.

Thompson and Colburn were invited to speak to a wide range of audiences about the ethics of warfare including at West Point, a conference in Norway, and at Connecticut College in New London, where they were each awarded an honorary doctorate.

[20] Thompson later served as a counselor in the Louisiana Department of Veterans Affairs, and gave a talk at the United States Naval Academy in 2003[22] and at West Point in 2005 on Professional Military Ethics.

Rose Manuscript, Archives, and Rare Book Library at Emory University holds a collection relating to the life and careers of Hugh Thompson and Lawrence Colburn.

"It was the ability to do the right thing even at the risk of their personal safety that guided these soldiers to do what they did", then-Major General Michael Ackerman said at the 1998 ceremony.

Later that year, both men served as co-chairs of STONEWALK, a group who pulled a one-ton rock engraved "Unknown Civilians Killed in War" from Boston to Arlington National Cemetery.

[25] His biography The Forgotten Hero of My Lai: The Hugh Thompson Story by Trent Angers[4] was included on the U.S. Army Chief of Staff's professional reading list.

[30] A subsequent solo piano work, Elegy for the Victims of My Lai, adapted from the concerto was recorded and performed by pianist Sasha Toperich.

[31] The Kronos Quartet used Berger's music along with a libretto by Harriet Scott Chessman to compose a "monodrama" with tenor Rinde Eckert.

[32] At the age of 62, after extensive treatment for cancer, Thompson was removed from life support and died on January 6, 2006, at the Veterans Affairs Medical Center in Pineville, Louisiana.