Captain McNamara was the pilot of a B-26B Invader bomber with the 729th Bomber Squadron, 452nd Bomber Wing. On 29 December 1950, while on a night intruder mission over Sunchon Air Base, North Korea, his aircraft was hit by anti-aircraft fire, crashed and burned. He was listed as Missing in Action and was presumed dead on 17 December 1951. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

McNamara was awarded the Air Medal, the Purple Heart, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.