NEW YORK (AP) — Lawrence Byrne, the New York Police Department’s top lawyer during a fraught period that followed a court ban on officers frisking people without cause, the chokehold death of Eric Garner and the revelation that police spied on law-abiding Muslims after 9/11, has died. He was 61.

Byrne, whose brother was a rookie NYPD officer when he was shot and killed in 1988, died Sunday at a Manhattan hospital after a heart attack Thursday, the police department said.

As deputy commissioner of legal matters from September 2014 until his retirement in July 2018, Byrne was at the forefront of policy changes and legal fights that affected everything from how officers walk the beat to the public's ability to know which ones were punished for misconduct.

Byrne defended the department in litigation over its spying on Muslims, which was uncovered in reporting by The Associated Press. He interpreted a state secrecy law in a way that shielded the disciplinary records of officers accused of brutality from public view. He embraced the use of administrative subpoenas to further investigations without a judge's approval. And he helped craft new policies after a court ruled that the practice known as stop-and-frisk was discriminatory and unconstitutional.

Byrne oversaw about 100 lawyers in the police department’s legal bureau and established a unit of about 30 lawyers designed to reduce the cost of lawsuits by investigating and defending officers against unfounded allegations.

“Larry Byrne systematically fought any effort at external oversight, be it through (public records requests), from the City Council, or the Mayor’s Office,” Albert Fox Cahn, the founder and executive director of the Surveillance Technology Oversight Project, told The Intercept in August. “He wanted the NYPD to be a self-governing entity.”

Byrne’s death left many people in law enforcement shocked and saddened.

Byrne had “great judgment” and “always had an empathy for the right things,” his longtime friend, former FBI Director Louis Freeh, said in a statement.

Police Commissioner Dermot Shea called Byrne a “tremendous attorney” and an "advocate for all of the people of New York City.”

“It’s just a real sad day for the NYPD,” Shea told WPIX-TV.

Byrne, a 1984 graduate of the New York University School of Law, was a federal prosecutor in Manhattan and in the U.S. Justice Department’s Criminal Division in Washington; worked at various law firms; and had two stints at a corporate risk assessment firm founded by Freeh — immediately before and after his time at the NYPD. Byrne was a director and senior adviser at the firm until last month, according to his LinkedIn profile.

At the NYPD, Byrne ended the practice of disclosing officers’ disciplinary records to the public, arguing that the department was actually barred from doing so by a state civil rights law. State lawmakers, spurred to action this year by protests over the police killing of George Floyd in Minneapolis and other police misconduct, repealed the secrecy law in June. Several public safety unions are fighting the law in court.

Byrne also defended the NYPD’s practice, exposed by reporting in the New York Daily News and ProPublica, of filing lawsuits under the state’s nuisance abatement law that had the effect of removing people from their homes even if they weren’t convicted of a crime.

“The law does not require criminal conviction, does not require (a) particular disposition of a criminal case, does not even require an arrest of anyone,” Byrne told the Daily News in 2015.

In 2018, just before retiring, Byrne informed the Justice Department that the NYPD would no longer wait for the end of a federal civil rights probe before bringing departmental charges against an officer whose chokehold caused the death of Eric Garner four years earlier. That officer, Daniel Pantaleo, ended up being fired after an internal disciplinary trial.

Byrne’s brother, Edward, was 22 when he was shot and killed at the behest of a jailed drug trafficker while sitting in a marked patrol car guarding the home of a witness in Queens in 1988. Their father, Matt, was an officer for 22 years.

Edward Byrne’s death garnered national attention. Former President George H.W. Bush carried his badge with him while running for the White House, and a major Justice Department grant program is named in his honor.

Over the years, Lawrence Byrne and his family have testified before the state parole board, urging it not to release the men who killed his brother.

“He worked tirelessly to ensure that his brother’s killers – and all cop-killers – never escaped justice," police union President Pat Lynch said in a statement.

Byrne’s survivors include his mother, brothers and three sons, the police department said. A funeral is scheduled for Friday at St. James Church in Seaford.