Charles “Chuck” Trimble, a former leader of the National Congress of American Indians and founder of the American Indian Press Association, has died at age 84.

The Oglala Lakota journalist and activist died of natural causes Monday in Omaha, Nebraska, his daughter, Kaiti Fenz-Trimble, said on Facebook.

Trimble was born in Wanblee, South Dakota, on the Pine Ridge Reservation, and attended the then-Holy Rosary Mission boarding school. He graduated from the University of South Dakota, served in the U.S. Army and later studied journalism at the University of Colorado.

Chuck Trimble Judith L. Cornelius via AP

Trimble founded the American Indian Press Association in the 1970s, citing a lack of coverage of Native American issues, Indian Country Today reported. It operated a news service for tribal newspapers across the U.S.

He was then elected executive director of the National Congress of American Indians, an organization established to protect tribes’ sovereign rights. He held the position from 1972 to 1978, calling it both a stressful and deeply rewarding time.

“I was fortunate to have served through the decade most prolific in the enactment of legislation for new policy, programs, and resources, as well as executive actions favorable to Indian tribes and off-reservation Indian communities,” Trimble wrote in an address for the group’s 2009 convention. “These included the Indian Self-Determination and Education Assistance Act, the Indian Financing Act, the Indian Health Care Improvement Act and unprecedented return of significant lands to tribes.”

Among his many accomplishments, Trimble helped start a newspaper on the Colville Reservation in Washington state to inform people about the implication of termination, the federal government’s effort from the 1940s to the 1960s to disband tribes, Indian Country Today reported. It chronicled the tribe’s eventual rejection of the policy.

He was also known for his columns on topics ranging from tribal politics and languages to aging.

“His passing has left a big hole in the field of Native American journalism,” Oglala Lakota journalist and publisher Tim Giago wrote in the Rapid City Journal.

Trimble was inducted into the South Dakota Hall of Fame in 2013 and received several honorary degrees.

Jack Marsh, former Argus Leader editor and Freedom Forum executive, said Trimble was admired by Native and non-Native journalists alike.

“He was an honorable, fine and decent man who did much to promote reconciliation and advance a greater understanding of Native people and Native issues,” Marsh said, according to Indian Country Today. “He was a role model for many in the field of media and journalism, including me, a gifted teacher and an excellent writer.”

In addition to his daughter and her husband, Trimble is survived by his wife, Anne.