The chief of the embattled U.S. Capitol Police department stepped down from his post on Friday, days earlier than he said he would following a deadly breach of the Capitol complex by a mob supporting President Trump.

Chief Steven Sund had said Thursday that his resignation would be effective Jan. 16, hours after House Speaker Nancy Pelosi (D-Calif.) publicly called on him to step down.

But Assistant Chief Yogananda D. Pittman took control of the agency on Friday, according to the agency’s website. A Capitol Police officer since 2001, she was one of the first Black female supervisors to become a captain. She led her unit in providing security for the 2013 presidential inauguration, the website says, and in 2018 was promoted to deputy chief.

The Capitol Police did not request significant help from other law enforcement agencies in advance of the siege, which unfolded as lawmakers attempted to certify the victory of President-elect Joe Biden. In an interview with The Washington Post on Sunday, Sund said he sought such help but was rebuffed by his bosses in Congress.

The department did not have enough of its own officers and fortifications — or a backup plan in place — to keep the rioters out of the building.

A Capitol Police officer, Brian D. Sicknick, died on Thursday after physically engaging the mob. Ashli Babbitt, who breached the building, was fatally shot by a Capitol Police officer during the confrontation; three others died of medical emergencies, officials have said.

And the agency took another hit Saturday, with the suicide of off-duty officer Howard “Howie” Liebengood, 51, the son and namesake of a former Senate sergeant at arms, lobbyist and Hill staffer.

The agency did not list a cause of when it announced Liebengood’s death on Sunday. But a spokesman for the family confirmed Monday that he died by suicide and had been on duty at the Capitol on Wednesday. Liebengood had been with the department since April 2005 and worked in the Senate Division.

A former co-worker said Liebengood was often posted at the Delaware entrance of the Russell Senate Office Building — his favorite assignment.

“We are reeling from the death of Officer Liebengood,” Gus Papathanasiou, head of the Capitol Police union, said in a statement. “Officer Liebengood was an example of the selfless service that is the hallmark of USCP.”

The Sunday statement from the Capitol Police says: “Our thoughts and prayers go out to his family, friends, and colleagues.”

The White House lowered its flag to half-staff on Jan. 10 to honor U.S. Capitol Police officer Brian D. Sicknick and off-duty officer Howard “Howie” Liebengood. (The Washington Post)

On Sunday, Trump ordered flags lowered to half-staff in honor of both Sicknick and Liebengood. Scores of officers lined up outside the Capitol and saluted as a hearse carrying Sicknick’s remains passed by.

On social media, there was a fresh outpouring of grief. Rep. Jennifer Wexton (D-Va.) posted on Twitter that she was “deeply saddened” over the death of Liebengood, who was her constituent. Former senator and secretary of state John F. Kerry (D-Mass.) called the deaths of Sicknick and Liebengood “a tragic loss of two patriots who spent their careers protecting the halls of democracy.”

Barry Pollack, a lawyer representing the Liebengood family, said in a statement that “Mr. Liebengood’s family members wish to grieve privately as they mourn the sudden and heartbreaking loss of Howard Liebengood.”

“He will be sorely missed,” the statement added. Liebengood is survived by his wife and siblings.

Friends described Liebengood as humble and reserved, and said he shared a love of racecar driving with his late father, as well as a pull toward the halls of the Capitol. He spent several years as a professional racecar driver until 2005, when he left the profession to become a Capitol Police officer.

Charlie Ostlund, 70, taught Liebengood at James Madison High School in Vienna, Va., in the 1980s, and was his wrestling coach. He remembered Liebengood as a team player who often surprised opponents with his strength and physical talent.

Ostlund said the younger Liebengood looked up to his father, Howard S. Liebengood Sr., who served from 1981 to 1983 as Senate sergeant at arms, charged with ensuring security in the Capitol and Senate buildings, as well as protecting members of the Senate.

In a 2003 interview with a motorsports website, the younger Liebengood said his parents were his biggest inspiration. My father “has accomplished so much in his professional career in government and the political arena,” he said at the time. “If I could accomplish an [eighth] of what he has accomplished, I would be very proud . . . he is my hero!”

Liebengood told his interviewer he was involved in the National Campaign to Stop Violence, an effort aimed at middle-schoolers.

“He was a great student and great kid,” Ostlund said. “This is just so, so sad.”

Liebengood Sr. left his post as sergeant at arms to become a lobbyist, eventually starting his own firm with another former Hill staffer. In 2001, he returned to Capitol Hill as chief of staff to his longtime friend, Sen. Fred D. Thompson (R-Tenn.), and later to then-Senate Majority Leader Bill Frist (R-Tenn.). He died of a heart attack on Jan. 13, 2005, two weeks shy of his planned retirement.

On the Senate floor after his death, Frist said the elder Liebengood “loved the Senate,” according to a 2005 transcript. “He loved the purpose of this institution; he loved its tradition; and, above all, he loved its people. The Senate was his extended family.”

A classmate and wrestling teammate of the younger Liebengood, Stu Wilkinson, said his friend’s relationship with Washington’s political elite dates back to their childhood — though he didn’t brag about it.

He recalled a school trip to the White House in the 1980s, when Secret Service officers took Liebengood aside to have him speak with then-Senate Majority Leader Howard Henry Baker Jr. (R-Tenn.).

“Here comes Senator Baker shaking Howie’s hand,” Wilkinson said. “[Liebengood] was so humble. . . . None of us had any clue how they knew each other.”

Wilkinson said that when he saw news reports of the Capitol riots on Wednesday, his mind went straight to Liebengood. He scanned the television footage, hoping his friend was all right. “He was an outstanding guy,” Wilkinson said. “A quiet, silent leader.”

Bill Beck, 80, was a close friend of Liebengood Sr. who watched his son grow up. At the Capitol, he said Sunday, both men strove to engage lawmakers and staffers regardless of political party.

On the day of the Capitol attack, Beck said, he emailed the younger Liebengood to see how he was doing. He didn’t hear the news of his death until Sunday.

“I knew him his whole life. He was a good human being,” Beck said. “After everything, this is just . . . it’s tragic.”

Carol D. Leonnig and Julie Tate contributed to this report.

If you or someone you know needs help, call the National Suicide Prevention Lifeline at 800-273-TALK (8255). You can also text a crisis counselor by messaging the Crisis Text Line at 741741.