ALBUQUERQUE, N.M.—Merril Sandoval's family always knew he was a Marine.

But it would be decades before they found out he was a member of the elite Navajo Code Talkers, a group of Navajo Marines who confounded the Japanese during World War II by transmitting messages in their native language.

Sandoval's health had been declining for a year, and the 82-year-old died at a Phoenix hospital Saturday, said his son, Gary Sandoval. Just last Friday, Merril Sandoval's spirits seemed high as he asked his family to bring him clothes and told them they'd go out to eat fish and chips.

"Just 18 hours later, he was dead. It was quite a shock to us," Gary Sandoval said Monday. "It's OK. We're happy he's in a good place now. The way Navajos think, he's gone on to a beautiful place."

Even as Merril Sandoval grew older, his family still was learning new things about their father and his experiences with the Code Talkers, who took part in every Marine assault in the Pacific from 1942 to 1945.

After the war, Code Talkers were told to keep their work secret. Not until after the information was declassified in 1968, did Sandoval's family learn of his deeds.

"He was telling stories I never even heard of," Gary Sandoval said. "That was our experience, we just never knew."

Sandoval was a freshman in high school when Marine recruiters visited him. His brother Samuel joined, but their father, Julian, said the 16-year-old Merril was too young and would have to wait another year.

Julian allowed Sandoval to enlist the following year, and said: "'You're a man, go find your brother and bring him home,'" Gary Sandoval said. "The thing is, he never did find him. They never worked together as Code Talkers."

At 17, Merril Sandoval boarded a train to Santa Fe, where he filled out his paperwork and completed a physical exam. After boot camp, he was transferred to Camp Pendleton to the Radio Communication School where he was trained as a Navajo Code Talker.

The Marines shipped Sandoval to Hawaii and, his son says, he "started island-hopping after that," to places like Saipan and Iwo Jima.

It was in Iwo Jima where Gary Sandoval said his father learned how to pray to God after his landing craft got hit and the radio company he was part of was thrown into the ocean. Sandoval swam about 100 yards to the shore and spent the next 24 hours on the beach under constant shelling by the Japanese, his son said.

"He says it was like being in a movie theater...He says he doesn't know how he made it through," Gary Sandoval said.

Merril Sandoval was discharged in March 1946, and returned to the United States to finish high school. He later worked as a machinist, a Navajo police officer and a legal advocate.

He also served as an interpreter for the Navajo courts.

In the 1980s, Sandoval began traveling across the country, telling stories of the Code Talkers.

"He was a great man," Gary Sandoval said. "He was so humble, and everybody liked him. He had friends all over the place, all over the country."

Merril Sandoval's daughter, Jeannie Sandoval of Espanola, said her father's stories always were "heartfelt, genuine and real."

"But he always said his heroes were those who didn't make it back," she said in a news release.

Navajo President Joe Shirley Jr. has ordered flags flown at half-staff on the reservation from Wednesday until Saturday in honor of Merril Sandoval.

Sandoval is survived by his wife, Lorraine Humetewa Shingoitewa Sandoval of Tuba City, Ariz; his son Gary Sandoval; daughters Jeannie Sandoval, Sharon Iron and Maxine Sandoval; and brothers Samuel Sandoval and Bert Sandoval.

He had 17 grandchildren, 22 great-grandchildren and one great-great grandchild.

Funeral arrangements are pending.