U.S. Transportation Secretary Elaine Chao announced she is resigning from President Donald Trump’s cabinet after supporters of the president breached the U.S. Capitol on Wednesday in protest of his election loss.

“Yesterday, our country experienced a traumatic and entirely avoidable event as supporters of the president stormed the Capitol building following a rally he addressed,” Chao said in a statement on Twitter. “As I’m sure is the case with many of you it has deeply troubled me in a way that I simply cannot set aside.”

Chao said she is resigning as of Jan. 11 and will help her announced successor, former South Bend, Ind., Mayor Pete Buttigieg, who was nominated by President-elect Joe Biden.

She is the first cabinet secretary to announce her departure after the events and joins a growing list of administration officials who have stepped down with two weeks before the end of Trump’s term, including former White House Chief of Staff Mick Mulvaney, who left his post as special envoy to Northern Ireland.

One government official said there may be additional cabinet resignations before Monday.

Congress was in the middle of arguing over objections to the electoral vote count from Arizona, an effort driven by a group of Republicans and encouraged by Trump, when lawmakers were forced to abruptly suspend the proceedings. Eventually they were hustled out of the House and Senate chambers by security as a mob surged into the Capitol, breaking windows and doors.

Chao, 67, who is married to Senate Majority Leader Mitch McConnell, a Kentucky Republican, was appointed by Trump in 2017. She previously led the Labor Department for the full eight years President George W. Bush was in office.

As secretary Chao has moved to loosen auto gas mileage standards, reduce consumer protections for airline passengers and to halt or relax numerous safety rules that had been under development in the prior administration.

The department has also taken steps to eliminate barriers to deployment of self-driving, while critics — including the National Transportation Safety Board — say regulators have failed to ensure the safety of autonomous vehicles being tested.

Her resignation was reported earlier by the Washington Post.

In a Dec. 31 Reuters interview, Chao had said she planned to remain on the job through Jan. 20 when Biden is due to take office.

Chao formerly was Deputy secretary of transportation and chairwoman of the Federal Maritime Commission.

She has also been chief executive officer of United Way of America and director of the Peace Corps. She worked as vice president of syndications at Bank of America Capital Markets Group and as a banker with Citicorp in New York.

Chao was the 18th transportation secretary in U.S. history, and the third woman to hold the post following Elizabeth Dole, who served under President Ronald Reagan, and Mary Peters, who served under George W. Bush.

Reuters contributed to this report.