Congressman Elijah Cummings died early Thursday, his office has announced.

Cummings, the powerful Democratic House Oversight and Reform Committee chairman, was a key figure in the impeachment inquiry into President Trump, a champion of civil rights and the Voting Rights Act, and has long been one of the most recognizable Democrats in Congress.

In a brief statement, Cummings’ office said the congressman passed away at 2:45 a.m. ET at his native Baltimore’s Johns Hopkins Hospital. The Baltimore Sun reported earlier this week that he didn’t return to work as expected this week following an unspecified medical procedure. Cummings had previously battled health issues with his heart.

His wife, Maya Rockeymoore Cummings, paid tribute early Thursday, expressing her love and celebrating his record of public service.

“Elijah Cummings was an honorable man who proudly served his district and the nation with dignity, integrity, compassion and humility. He worked until his last breath because he believed our democracy was the highest and best expression of our collective humanity and that our nation’s diversity was our promise, not our problem. It’s been an honor to walk by his side on this incredible journey. I loved him deeply and will miss him dearly.”

Cummings served as the representative for Maryland’s 7th Congressional District from 1996 until his death. He was a frequent adversary of Trump and they had a high-profile clash just three months ago, after the president called Baltimore a “disgusting, rat and rodent infested mess.” Trump later appeared to mock on Twitter a late-night burglary attempt at his home.

Cummings refused to respond in kind, offering instead to take Trump on a tour of the city “to see all the wonderful things that are happening.” “I’ll ride with him for hours if he asked to,” he said.

Cummings was among the three Democratic committee chairmen who signed a letter last month that accompanied a congressional subpoena of Secretary of State Mike Pompeo, who has so far declined to testify in the ongoing impeachment inquiry of the president.

Following the testimony of Special Counsel Robert Mueller in July, Cummings said: “I’m begging the American people to pay attention to what is going on. Because if you want to have a democracy intact for your children, and your children’s children, and generations yet unborn we've got to guard this moment… this is our watch.”

In late September, as Trump made clear his support for his officials’ attempts to dig up dirt on his potential 2020 rival Joe Biden, Cummings went public with his support of impeachment. His statement about his decision began: “When the history books are written about this tumultuous era, I want them to show that I was among those in the House of Representatives who stood up to lawlessness and tyranny.”

Prior to the Trump era, he was best known for his work defending the Voting Rights Act. In an interview with Politico when he was taking the helm of the House Oversight Committee, he recalled his mother, who had recently died, and her experiences of segregated Baltimore in the 1940s.

“My mother, on her dying bed, the last thing she said to me was, ‘Do not let them take away our right to vote.’ And then she died. Why? Because she had seen the pain that people had gone through to get the vote, what it meant to see for her,” Cummings said in October last year.