San Francisco District Attorney George Gascon on Thursday announced his resignation and said he is moving to Los Angeles to explore a run for top prosecutor there.

Gascon informed his staff at an afternoon meeting before submitting a formal letter of resignation to San Francisco Mayor London Breed.

Gascon had previously signaled an interest in returning to Los Angeles, where he once served in the highest ranks of the city’s police department, the Los Angeles Times reported.

He said in January that he would not seek a third term in the Bay Area, and in the following months he held several community meetings in the Los Angeles area to discuss criminal justice topics.

If Gascon tries to unseat Los Angeles County District Attorney Jackie Lacey, the race could be the largest test yet of a nationwide push to elect progressive-minded law enforcement officials, the Times said.

Lacey is popular with law enforcement but has faced growing criticism from the left over several issues, notably her perceived reluctance to hold law enforcement officials accountable for accusations of misconduct and excessive force.

“Making our communities safer and more equitable remains my life’s work, and I’m simply not ready to slow down and put public service behind me,” Gascon wrote in Thursday’s letter.

First appointed in 2011, Gascon’s second term would have finished at the end of the year.

The deadline for candidates to enter the Los Angeles race is in early December. Gascon’s last day in office in San Francisco will be Oct. 18, according to the letter.

His chief of staff, Cristine Soto DeBerry, will take over as San Francisco’s interim district attorney, according to the newspaper.