New York City Police Commissioner Keechant Sewell, the first woman to hold the position, is stepping down after 18 months on the job.

Sewell, who was appointed by Mayor Eric Adams, announced the resignation in an email to department staff Monday afternoon.

“While my time here will come to a close, I will never step away from advocacy and support for the NYPD, and I will always be a champion for the people of New York City,” she wrote.

Adams, a Democrat, confirmed the move in a statement, thanking Sewell for her “steadfast leadership.”

Sewell took over as commissioner when Adams, a former NYPD captain, became mayor in January 2022, having pledged beforehand to name a woman to the post.

During her brief tenure, she oversaw a decrease in some categories of crime – including murders – while contending with several high-profile crises, including the fatal shooting of two officers during her first month on the job. In a statement, Patrick Lynch, the president of the Police Benevolent Association, said her leadership would be “sorely missed.” Sewell shied from New York’s spotlight, rarely making herself available to press, even as Adams has made crime-fighting a centerpiece of his administration.

She also faced speculation that she was not truly in control of the department, fueled in part by Adams’ decision to appoint a former NYPD chief and key ally, Phillip Banks, as a deputy mayor of public safety. Banks has been holding weekly public briefings on crime, often without Sewell in attendance.

NYPD commissioners often serve abbreviated tenures in one of the highest-pressure, most politically challenging jobs in policing. Sewell’s predecessor, Dermot Shea, was in the post for two years. His predecessor, James O’Neill, lasted three. Before that, William Bratton served less than three years in his second stint as commissioner, having served for just over two years under Mayor Rudy Giuliani.

The notable exception is former commissioner Raymond Kelly, who served for 16 months under former Mayor David Dinkins, then returned and was commissioner for all 12 years that Michael Bloomberg was mayor.

Sewell started with the Nassau County Police Department as a patrol officer in 1997, then became a precinct commander, head of major cases, a top hostage negotiator and finally chief of detectives, where she oversaw a staff of about 350 — about 1% the size of the NYPD’s unformed ranks.

In his statement, Adams said Sewell deserved credit for combatting crime in New York City.

“The commissioner worked nearly 24 hours a day, seven days a week for a year and a half, and we are all grateful for her service. New Yorkers owe her a debt of gratitude.”

The Adams’ administration has seen a series of high-profile departures in recent weeks, including his top housing official, Jessica Katz, and the city’s efficiency officer, Melanie La Rocca.