US Senator Olympia Snowe said an Army captain from Maine has died while serving in South Korea. Snowe said in a statement released over the weekend that 30-year-old David Haas, of Brunswick, died Friday. She did not release the cause of his death. Snowe said in the statement, ‘‘He defended this country with limitless courage, and we owe him, and his family, a debt of immeasurable gratitude that we can never repay, and must never forget.’’ Haas had served two tours in Iraq. In South Korea, he served with the 403d Field Support Brigade. He was a graduate of Brunswick High School and the University of Richmond in Virginia.