Former Rep. William H. Gray (D-Pa.), the first African-American to chair the House Budget Committee and the first to serve as majority whip, passed away Monday in London. He was 71 years old.

Gray, a six-term congressman who represented Philadelphia, resigned from Congress in 1991 to serve as the president of the United Negro College Fund. He was a co-founder of the Washington, D.C., lobbying firm Gray Loeffler LLC, and he continued in the family business, serving as the pastor at Bright Hope Baptist Church in North Philadelphia, where his father once led the congregation.

An icon of Philadelphia politics, Gray's tenure in Congress was highlighted by his fight against apartheid, as he pressed the U.S. to limit funding to South Africa.

In a statement released Monday night, House Minority Leader Nancy Pelosi (D-Calif.) heralded the congressman as "a giant."

"He was a leader and a trailblazer, a proud representative of the people of Philadelphia, a man who left his mark on the history of his city. His time in Congress was an extension of the family business: serving the community, acting on the values of his faith, giving back to his neighbors and to the less fortunate," Pelosi said.

"To serve alongside Bill Gray was to be inspired by his passion and commitment, by his focus on the future and his belief in the common good. It was an honor and a privilege to know him as a colleague and a friend."

President Obama echoed Pelosi, calling Gray a "trailblazer" in a statement.

"Bill's extraordinary leadership, on issues from housing to transportation to supporting efforts that ended Apartheid in South Africa, made our communities, our country and our world a more just place," Obama said.

Sen. Bob CaseyRobert (Bob) Patrick CaseyDem senator: Inaction on gun control sending 'unintentional endorsement' Congress has a chance to make saving for college a lot easier Sen. Manchin won’t vote for Trump’s mine safety nominee MORE (D-Pa.) said in a statement that Gray was "a trailblazer for a new generation of African American elected officials."

Gray was attending the Wimbledon Championships in London and died suddenly of what appear to be natural causes, according to NBC News.

Philadelphia Mayor Michael Nutter said in a statement that during his time in the House, Gray "utilized his position to influence public policy and federal spending unlike anything we’ve seen in modern times."

"In the chess match of politics, he knew how to get things done," Nutter continued. "He could charm you or twist your arm as needed, but it was always in the best interests of the constituents he served."

This post was updated at 12:18 p.m. on July 2.