The photojournalist Michel du Cille, three-time winner of the Pulitzer Prize, died unexpectedly on Thursday of a heart attack while on assignment in Liberia.

The Washington Post, where du Cille worked for more than two decades, reported that the photographer collapsed while returning on foot from a village in Bong County that has been affected by Ebola. Du Cille collapsed and remained unconscious. He was then taken to a nearby clinic where he experienced difficulty breathing. He was pronounced dead upon arriving at Phebe Hospital, two hours away. A Washington Post spokeswoman emphasized that there was no connection between du Cille’s death and the Ebola outbreak.

Du Cille was awarded his first Pulitzer in 1985 for his coverage of a volcano eruption in Colombia. He joined the Washington Post in 1988 and worked for the newspaper for the next 26 years, including stints as director of photography and assistant managing editor, before returning to the field to resume his work as a full-time photographer.

Many of du Cille’s co-workers have expressed their sadness at the loss of their friend and talented colleague.

“Michel died at 58 doing the work he loved,” Marty Baron, executive editor of the Washington Post, said in a memorandum for members of staff. “He was completely devoted to the story of Ebola, and he was determined to stay on the story despite its risks. That is the sort of courage and passion he displayed throughout his career.” Baron also called du Cille “one of the world’s great photographers.”