In 1970, Thompson testified against those responsible for the Mỹ Lai Massacre. Twenty-six officers and enlisted soldiers, including William Calley and Ernest Medina, were charged with criminal offenses, but all were either acquitted or pardoned. 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. As a direct result of what he experienced, Thompson experienced posttraumatic stress disorder, alcoholism, divorce, and severe nightmare disorder. Despite the adversity he faced, he remained in the United States Army until November 1, 1983, then continued to make a living as a helicopter pilot in the Southeastern United States.