Rep. Elijah Cummings, D-Maryland, who was serving as chair of the House Committee on Oversight and Reform, died Thursday morning. He was 68.

Rep. Katie Hill, D-Agua Dulce, who has served as vice chair of the same committee, served alongside Cummings during her first 10 months in office.

She issued the following statement about Cummings, whom she called a “friend, adviser and a leader,” in response to his passing:

“He has been called the North Star of this Congress and I could not agree more — he was singularly principled and I’m deeply thankful for his mentorship.”

The committee member with the most seniority, Carolyn Maloney, D-New York, will now serve as acting chair, according to Kassie King, communications director for Hill.

Cummings was also a key figure in the effort to seek an impeachment hearing against President Donald Trump, who shared the following statement in response to his passing:

“My warmest condolences to the family and many friends of Congressman Elijah Cummings. I got to see firsthand the strength, passion and wisdom of this highly respected political leader. His work and voice on so many fronts will be very hard, if not impossible, to replace!”