(NEXSTAR) – Johnny Grier, the National Football League’s first Black referee, has died at the age of 74.

Troy Vincent, Sr., the league’s executive vice president of football operations, confirmed the news on Twitter Wednesday, calling Grier “a trailblazer who paved the way for those in the field of NFL officiating and beyond.” It wasn’t immediately clear what the cause of death was.

Grier started as a field judge and worked at Super Bowl XXII in 1988, during which Doug Williams, the first Black starting quarterback to win a Super Bowl, defeated John Elway’s Denver Broncos at Jack Murphy Stadium in San Diego.

The next season Grier was promoted to referee, according to the NFL; his career would span 24 years.

Grier was born in North Carolina and went to college at the University of the District of Columbia, according to Football Zebras, a site that covers NFL officiating. After a few years of officiating high school and college games, Grier joined the NFL in 1981 at the age of 34.

Grier worked 15 playoff games, including as a referee during the 1993 AFC Championship between the Bills and Chiefs.

He was known for his calm, but firm approach to officiating, according to Football Zebras. Grier was forced to retire after suffering a leg injury but went on to join the Mid-Eastern Athletic Conference as the supervisor of officials.

“Rest in peace to a true pioneer of the game, Johnny Grier,” the NFL tweeted.