New York City Police Commissioner William Bratton will retire in September, Mayor Bill de Blasio announced Tuesday.

He will be replaced by NYPDs Chief of Department James ONeill.

Bratton, who was appointed by de Blasio in 2014, previously said he planned to step down by the end of 2017 . He will take a job in the private sector.

Under Bratton, theres been a dramatic reduction in the use of stop-and-frisk by New York police officers and crime levels are at historic lows. But Brattons latest tenure at the top of the NYPD he previously served as commissioner from 1994 to 1996 has also been marked by the police killings of unarmed black men like Eric Garner and Akai Gurley.

Its a crisis in America at this moment, Bratton said Tuesday of race relations in the country. He added that hes reluctantly resigning.

I wish I had more time chronologically, he said.

Brattons career saw the rise of the so-called broken windows theory, which he championed as former Mayor Rudy Giulianis police commissioner. Under that strategy, officers aggressively enforced low-level offenses like vandalism to reduce New Yorks high crime rate. But that model has been criticized for disproportionately targeting African-Americans and Latinos.

Bratton leaves behind a complicated legacy: while he started the NYPD down the road to curbing its worst stop-and-frisk excesses and abuse, he is also the architect of broken windows policing, which has caused similar harms to many of the same communities, said Center for Constitutional Rights attorney Darius Charney in a statement.

De Blasio on Tuesday praised Bratton as he prepared to exit the department. Brattons contributions are literally inestimable and extraordinary, de Blasio said, though he also noted that work has a long way to go to improve the NYPDs relationship with residents around the city.

The mayor said Bratton notified him on July 8 that he would resign, and that recent protests and investigations into alleged corruption had nothing to do with the announcement.

Bratton drew the ire of civil rights advocates when he criticized the Black Lives Matter movement as leaderless and called on protesters to stop yelling and screaming at police.

Unlike the civil rights movement, which focused on the broad needs of desegregation and a segregated country, the needs of jobs, the needs of voting rights, the needs of education, the Black Lives Matter movement has focused entirely on police, and is not engaging in dialogue, instead engaging in protests where theres a lot of yelling and screaming, Bratton told WABC radio last month.

About 200 protesters, many allied with the Black Lives Matter movement, called for Brattons ouster in a rally Monday in Manhattans City Hall Park. They also called for the defunding of the NYPD.

ONeill, who joined the department in 1983, helped direct its attempt to improve strained relations with communities, de Blasio said.