Washington Post reporter Clarence Williams looks back on the career of D.C. Police Chief Cathy L. Lanier, who announced Tuesday that she will retire next month to take over as head of security for the National Football League. (Whitney Leaming/The Washington Post)

Washington Post reporter Clarence Williams looks back on the career of D.C. Police Chief Cathy L. Lanier, who announced Tuesday that she will retire next month to take over as head of security for the National Football League. (Whitney Leaming/The Washington Post)

When Muriel E. Bowser was sworn in as the District’s mayor in 2015, she was whisked onto national television — flanked by Kaya Henderson, the city’s schools chancellor, and Cathy Lanier, the District’s longtime and popular police chief. The District had the novelty of being the only major U.S. city with women in all three posts.

But with Lanier’s early retirement on Tuesday – and Henderson’s impending exit, announced two months ago — Bowser is losing two important partners. She now is looking for executives in public safety and education, both keys to the city’s recent economic expansion and growing population.

The departures, coming so close together, have presented Bowser with a defining moment in her second year as mayor. Bowser must replace two of the most public – and trusted – faces of the D.C. government over the past decade.

In an interview, Bowser said she was thankful that Lanier and Henderson had stayed through the beginning of her term. “I knew that we had great leaders, but I also knew they were not at the beginning of their tenures but toward the end,” she said.

Standing beside Lanier on Tuesday during the retirement announcement at police headquarters, the mayor thanked the police chief and said she was confident that she will find a replacement to carry on the chief’s legacy.

1 of 35 Full Screen Autoplay Close Skip Ad × The career of D.C. Police Chief Cathy L. Lanier View Photos Police Chief Lanier will resign to take over as head of security for the National Football League, ending 26 years on the force. Caption Police Chief Lanier will resign to take over as head of security for the National Football League, ending 26 years on the force. Aug. 16, 2016 D.C. Police Chief Cathy L. Lanier, right, and Mayor Muriel E. Bowser walk down the hall to announce Lanier’s resignation at a news conference at the Metropolitan Police Department headquarters in Washington. Jabin Botsford/The Washington Post Buy Photo Wait 1 second to continue.

[The biggest events — and challenges — in Cathy Lanier’s tenure]

Bowser signaled that the hire for police chief might come from within the department, saying that Lanier had done a great job grooming talented leaders.

“For the police department, this is an agency I know very, very well. As an ANC commissioner, ward council member and mayor, I spent a lot of time with the folks in the room,” Bowser said. “But we will recruit the right leader. I don’t have an immediate plan. I don’t think we’re going to need the services of a search firm” to look nationally.

But Bowser said she will continue the nationwide search for a schools chancellor and continue listening to residents at community meetings.

Meanwhile, the mayor said she expects to promote someone from within for a third major vacancy in her cabinet, following the surprise resignation last week of Christopher Weaver, director of the Department of General Services. Bowser said she expects to elevate Greer Johnson Gillis to head of the agency in charge of most city building projects.

Bowser’s nominees to replace Lanier and Henderson will likely face intense examination from an increasingly adversarial D.C. Council.

Council member Kenyan R. McDuffie (D-Ward 5), who would direct nomination hearings for police chief, said Bowser must find a chief with a breadth of experience as well as an understanding of the unique, overlapping law enforcement agencies that operate in the nation’s capital.

“The stakes are incredibly high for the District of Columbia to ensure that we have the highest-quality chancellor as well as a police chief, given the critical role these two play,” he said.

Council Chairman Phil Mendelson said that a new police chief must be a skilled communicator able to connect with the community, especially against a national backdrop of protests and allegations of racial profiling that so far have not affected the District.

He also said the next chief must “obviously” deal with the city’s increase in homicides.

“I’m a strong believer in the value of stability, I think [former Chief Charles] Ramsey did a lot to turn around the department,” he said. “Cathy took it the next step, and now there’s the challenge and the opportunity to take it further.”

Mendelson wouldn’t say whether he thought the nomination process might overshadow other legislation under council review, such as a plan to tax businesses to provide paid family leave for private employees.

“The chief has to become one of our top priorities,” Mendelson said. “Will it displace others? I don’t know.”

Several council members cautioned that Bowser has nominated candidates for other positions who have not fared well, inviting even more scrutiny to the two highest-profile positions.

James Edward Kyle, Bowser’s choice for chief executive of St. Elizabeth’s Hospital for psychiatric treatment, resigned in April amid questions about his time leading a hospital later deemed unsafe by federal officials.

The mayor’s head of Emergency Medical Services resigned last winter, leaving the agency scrambling to replace her. A review showed she had resigned from her previous job over a perceived conflict.

And days into office, Bowser elevated a former Gray administration official to lead the Department of Veterans Affairs. He was quickly fired for an alleged inappropriate sexual encounter in a District office.

Mendelson and McDuffie said they were not sure whether a new police chief could be vetted before the end of the year.

If not, Bowser’s choice could face more questions next year when at least three new members will be seated on the council, including two who have been critical of the mayor’s response to last year’s 54 percent spike in homicides.

Former mayor Vincent C. Gray could be on the council, representing Ward 7, where homicides have tripled.

Trayon White, the Democratic nominee for the Ward 8 Council seat, has criticized Bowser for proposing more aggressive policing of former violent offenders.

Ronald L. Moten, co-founder of the anti-violence youth group Peaceoholics, said that Lanier’s leadership led to positive relationships with the community that helped reduce crime.

Her successor, he said, should be “a culturally competent native person ready to deal with a more diverse city with the understanding they must do the right things for the right reason so that our city can get the right results.”

Ann Marimow and Clarence Williams contributed to this report.