SOUTH THOMASTON – The death Thursday night of Ed Sleeper, an aviator and former Knox County commissioner, left those knew him shocked.

Though Sleeper was 67, his friends described him as full of vitality, apparently healthy and living an active life.

Doctors discovered within the past two weeks that Sleeper was suffering from an aggressive form of leukemia.

After being re-elected as selectman in South Thomaston late last month, he suffered a nosebleed that would not stop.

After seeking treatment at Penobscot Bay Medical Center in Rockport, he was transferred to Maine Medical Center in Portland, where he died.

“He was a wonderful and kind-hearted man who dedicated much of his life [to] helping others,” said U.S. Sen. Susan Collins in a statement.

Sleeper grew up in Rockland, but left after joining the Air Force. He rose to the rank of colonel and then and flew C-130s, Kevin Waters, director of operations and chief pilot at Maine Atlantic Aviation in Owls Head, said Friday.

Near the end of his career in the Air Force, Sleeper worked as a liaison to U.S. embassies in Scandinavian countries. After retiring, he returned to Maine.

He flew his own small plane from Knox County Regional Airport in Owls Head, and worked part-time for Telford Aviation, which later became Maine Atlantic Aviation, shuttling people to and from Matinicus, Vinalhaven, North Haven and Islesboro, among other places.

Sleeper also served as a flight instructor, Waters said, and was a Federal Aviation Administration check airman, responsible for monitoring other pilots.

“He was a role model for me,” Waters said.

Sleeper volunteered as a pilot with Angel Flight, donating his time and his aircraft to take patients to medical treatment facilities in Boston and elsewhere.

Waters said Sleeper was on a list of pilots who backed up LifeFlight Maine, and, even when weather was poor, his was the first hand to go up to volunteer to fly an emergency flight to the Penobscot Bay islands.

“He’d do whatever it takes to help someone out,” Waters said.

Sleeper served as a Knox County commissioner from 1997 to 2000. He ran unsuccessfully for state Senate in 1994.

Commissioner Lawrence Nash, with whom he served, said Sleeper was “a man who always tried to make the world a better place to live in,” by serving in the military, on the county board and as selectman in his town.

County Clerk Virginia Lindsey, who has worked for commissioners for 20 years, said Sleeper was among a handful of officials who stood out. “I learned a lot from him,” she said. “I’m heart-broken.”

Politically, Sleeper incurred the wrath of those opposing improvements at the airport. He was often single-minded in his support for improvements, and his enthusiasm for flying sometimes chafed those who wanted the airport to remain a sleepy, rural airfield, which most likely led to his losing his re-election bid.

After the defeat, he threw himself into other county service as chairman of the budget committee and as a member of the charter commission and the airport advisory committee.

Gene Kenniston served with Sleeper as a commissioner, and the two had known each other since grade school.

“He was just plain full of fun and able to poke fun at almost anything,” he said Friday. In school, “he was just too darn smart,” and ended up being the ringleader for mischief.

Sleeper and his wife, Astri, were high school sweethearts, Kenniston said.

“He was a brilliant guy,” Kenniston said.

A funeral is planned for 2 p.m. Tuesday, April 13, at Rockland Congregational Church.