For 37 years, Delouise Guerra never knew for certain what happened to the young man she called her baby brother, an 18-year-old Marine from Colorado who was missing and presumed dead after a helicopter crash on the other side of the world. The Defense Department told Guerra two months ago it had positively identified the remains of the man she called her baby brother, Pfc. James Jacques. The Colorado Marine was killed during the rescue of the crew of the S.S. Mayaguez, an American cargo ship seized by Cambodia's Khmer Rouge two days earlier on May 12, 1975. "Oh my God, it's a relief to know that they have found his final remains," Guerra said. It's just an honor to bring him home. Jacques will be buried with full military honors at Fort Logan National Cemetery in Denver on Tuesday on what would have been his 56th birthday. Jacques - pronounced "HAW-kas" - was among hundreds of Marines and airmen sent to storm Koh Tang Island, about 60 miles off the coast of Cambodia, to rescue the Mayaguez crew. A helicopter carrying Jacques and 25 others crashed into the surf off Koh Tang Island amid unexpectedly heavy fire from Cambodian fighters. Half the men on the helicopter were rescued, but the other 13 were declared missing, including Jacques. All 39 crew Mayaguez members were released safely by Cambodia, but some 40 U.S. servicemen were killed. Jacques' identification dog tags were found in 1992, but his remains weren't positively identified until this year, said Air Force Maj. Carie Parker of the Defense Prisoner of War and Missing Personnel Office. A Cambodian had turned over the remains to a U.S.-Cambodian search team in 2007. Newly available DNA technology allowed researchers to confirm the identity this year. Guerra got the news in a letter from the Marines that arrived at her Denver home on Aug. 14. Her son Bob was with her. "I started crying because I knew it was about my brother," she said. We were crying, we jumped, we hollered. Guerra, now 71, was 15 when Jacques was born. "He was a very loving, very caring - well, he was my baby brother," she said. He was just a really good person. Jacques grew up in La Junta, a small town about 140 miles southeast of Denver. He joined the Marines in October 1974, shortly after his 18th birthday. His family was apprehensive but didn't try to dissuade him, Guerra said. "It was something he wanted to do," Guerra said. He wanted to go and serve his country and do his best. He died just seven months after enlisting. Twelve of the 13 missing servicemen are now confirmed to have died, Parker said. She said she could not discuss the 13th because an investigation is ongoing. The Mayaguez operation is considered the last U.S. military engagement in Southeast Asia after the long and bloody war in Vietnam. The last U.S. combat troops left South Vietnam in 1973, and the South Vietnamese capital fell to North Vietnam on April 30, 1975, just two weeks before the Mayaguez engagement. Follow Dan Elliott at http://twitter.com/DanElliottAP