Atis Karlis Lielmanis was born in Latvia on January 2, 1939. He and his family came to the United States in 1950 and settled in Quakertown. After his 18th birthday, Lielmanis became a naturalized citizen. He graduated from Quakertown High School in 1957, where he played on the vollyball, basketball, cross-country, and chess teams.He was also the art editor for the school magazine. Upon graduation, he attended Lehigh University before enlisting in the Air Force in 1958. He received his commission in 1961.

On November 24, 1963, Lielmanis was serving as an Advisor-Navigator of a B-26B Marauder bomber aircraft in the 1st Air Commando Squadron, 34th Tactical Group, Bien Hoa Air Base, Vietnam. His aircraft was purposely exposed during a low-level Fight over hidden Viet Cong machine gun installations. After three passes on the target, the aircraft was badly damaged by enemy fire, causing it to crash. However, the Viet Cong positions had been revealed and were destroyed by cover aircraft. For his actions, Lielmanis’ was posthumously awarded the U.S. Air Force’s second highest award for valor, the Air Force Cross.

Lielmanis is buried at the historic Rahway Cemetery in Rahway, NJ.