Former fighter Stephan Bonnar, who played a significant role in the UFC’s growth into the dominant promotion in mixed martial arts, has died, UFC announced. He was 45.

Bonnar, who was inducted into the UFC’s Hall of Fame in 2013, died Thursday from “presumed heart complications while at work,” according to a statement from UFC on Saturday. No further details were released.

Bonnar, who originally was from Indiana, hadn’t fought in the UFC since 2014, and he went just 8-6 during seven years with the promotion.

He was a contestant in 2005 on the first season of “The Ultimate Fighter,” the UFC’s long-running reality competition show. He reached the competition’s finale, where he had a spectacular, bloody brawl with Forrest Griffin.

Griffin won the decision, but the viral attention gained by the highly entertaining bout is widely credited with exposing the little-known sport to a larger worldwide audience online and on Spike TV, which broadcast it.

“Stephan Bonnar was one of the most important fighters to ever compete in the Octagon,” UFC president Dana White said in the statement. “His fight with Forrest Griffin changed the sport forever, and he will never be forgotten. The fans loved him, related to him and he always gave them his best. He will be missed.”