On Nov. 3, 1969, the menand six Vietnamese soldiers were part of a Special Forces reconnaissance patrol operating in Quang Tri Province, near the Vietnam-Laos border. The patrol was ambushed by enemy forces and all three Americans were wounded. Brown was reported to have suffered a gunshot wound to his side. Due to heavy enemy presence and poor weather conditions, the search-and-rescue team was not able to reach the site until eight days later. At that time, they found military equipment belonging to Shue, but no other signs of the men.
Between 1993 and 2010, joint United States/Socialist Republic of Vietnam (S.R.V.) teams, led by the Joint POW/MIA Accounting Command (JPAC), conducted multiple interviews on nine different occasions in Quang Tri Province. Additionally, the S.R.V. teams unilaterally investigated this case, but were unable to develop new leads. Among those interviewed by the joint teams were former Vietnamese militiamen who claimed in 1969 they ambushed three Americans in the area near the Laos-Vietnam border. In 2007, a Vietnamese citizen led investigators to human remains that he had discovered and buried near the site of the ambush. In 2008, a military identification tag for Brown was turned over to the U.S. Government from a U.S. citizen with ties to Vietnam. Finally, in April 2010, joint teams excavated a hilltop area near Huong Lap Village, recovering additional human remains, military equipment, another military identification tag for Brown, and a “Zippo” lighter bearing the name ”Donald M. Shue” and the date “1969.”