The Justice Department will launch a federal civil rights investigation after a Staten Island grand jury declined to bring charges in the case of Eric Garner, an African American who died this summer after a white New York City police officer placed him in an apparent chokehold during an arrest.

As protesters gathered in New York, Attorney General Eric H. Holder Jr. announced an “independent, thorough, fair, and expeditious investigation,” which Garner’s family and activists have called for in recent months.

Holder called Garner’s July 17 death “a tragedy” and “one of several recent incidents across our great country that tested our sense of trust” in law enforcement.

The grand jury’s decision, announced Wednesday, follows a similar finding by a panel of jurors in Missouri in the case of Darren Wilson, the white police officer who fatally shot black teenager Michael Brown. The Missouri decision, announced last week, prompted days of demonstrations in scores of cities.

New York authorities have braced for similar unrest after the decision in the Staten Island case, emphasizing their intention to allow peaceful protest.

President Obama, speaking at an event in Washington, declined to make specific comments about the Staten Island grand jury’s decision, referring instead to his plans to promote better relations between police and the citizens they serve. “We are not going to let up until we see a strengthening of the trust and a strengthening of the accountability that exists between our communities and our law enforcement,” Obama said.

Garner, 43, died July 17 after Officer Daniel Pantaleo placed him in what appeared to be a chokehold during an arrest that was recorded on videos, which have contributed to public anger over the treatment of African American men by police.

Garner’s mother, Gwen Carr, expressed outrage at the decision. “I don’t know what video they were looking at, not the same one as the rest of the world,” Carr said at a press conference. “How could we put our trust in the justice system when they fail us like this?”

Eric Garner’s widow, Esaw, said on MSNBC that “it was like a modern-day lynching. They had it out for him.”

Carr welcomed the federal investigation and called for nonviolence. “Yes, we want you to rally, but do it in peace. Make a statement, but make it in peace.” Rev. Al Sharpton called for a national march next week in Washington, D.C., as a response to the Garner and Brown cases.

Pantaleo commented on the decision in a statement released through the NYC Patrolmen’s Benevolent Association. “I became a police officer to help people and to protect those who can’t protect themselves,” he said. “It is never my intention to harm anyone and I feel very bad about the death of Mr. Garner. My family and I include him and his family in our prayers and I hope that they will accept my personal condolences for their loss.”

When asked at a press conference about whether she accepted Pantaleo’s apology, Esaw Garner flatly declared: “Hell no.”

“The time for remorse would have been when my husband was yelling to breathe. That would have been the time for him to show some type of remorse or some type of care for another human being’s life—when he was screaming 11 times that he can’t breathe,” Esaw Garner said.  “There’s nothing that him or his prayers or anything else will make me feel any different. No, I don’t accept his apology. No, I can care less about his condolences. He’s still working, still getting a paycheck, still feeding is kids when my husband is six feet under and I’m looking for a way to feed my kids now.”

The NYPD bans the use of the chokehold; Pantaleo’s attorney, Stuart London, argued that the officer used an approved take-down move, which he learned in police academy, because Garner was resisting arrest.  “There was no pressure ever applied to his throat or neck area,” London said.

The New York City medical examiner’s office has classified Garner’s death as homicide due to “compression of chest and prone positioning during physical restraint by police.” The office also mentioned Garner’s asthma and hypertensive cardiovascular disease as contributing factors.

London said Pantaleo remains on modified assignment on Staten Island.

Holder said the majority of officers perform “honorably” and “it’s for their sake as well that we must seek to heal the breakdown in trust.” U.S. Attorney Loretta Lynch, who has been nominated to succeed Holder as attorney general, had been monitoring the case prior to Holder’s announcement, an official said.

The federal probe will include a review of the materials gathered during the local grand jury investigation.

After a meeting with officials, clergy and activists on Staten Island, de Blasio called for peaceful demonstrations. “It’s a very emotional day for our city. It’s a very painful day for so many New Yorkers — that is a core reality,” the mayor said. “We’re grieving again over the loss of Eric Garner.”

The NYPD will conduct an internal investigation, de Blasio said. Earlier Wednesday, New York’s two U.S. senators, Charles Schumer (D) and Kirsten Gillibrand (D), had said they would urge the Justice Department to investigate.

Protests had been planned in advance of the grand jury decision. Shortly after several outlets reported that the grand jury declined to indict, activists on Twitter quickly spread the word about protests set to take place late Wednesday afternoon and into the evening, including at Times Square.

New York Gov. Andrew M. Cuomo (D) also called for peaceful protests, saying in a statement: “While there will be people who disagree with today’s grand jury decision, it is important that we respect the legal process and rule of law.”

A pair of widely circulated videos emerged this summer showing the circumstances of Garner’s death. In the first, obtained by the New York Daily News, Garner is approached by officers apparently because he was selling loose cigarettes. After a confrontation, one officer places Garner in what looks very much like a chokehold. The man, who was asthmatic, then repeatedly tells the officer that he cannot breathe.

A second video shows Garner lying motionless on the ground for several minutes as officers wait for emergency personnel.

Other officers present on July 17 were not facing indictment as they were offered immunity in exchange for testimony.

Authorities may make public evidence considered by the grand jury. Richmond County District Attorney Daniel M. Donovan Jr. is seeking a court order that would allow him to release “specific information in connection with this grand jury investigation,” a statement read.

According to Donovan’s office, “over 38 interviews were conducted, yielding 22 civilian witnesses who reported to have seen some part of the interaction between Eric Garner and members of the NYPD.”

Donovan impaneled the 23-member grand jury this summer to determine whether Pantaleo would face charges. Donovan had not commented on which charges the grand jury considered. Before the decision, legal experts told the New York Times that the grand jury might consider lesser homicide charges, including second-degree manslaughter and criminally negligent homicide.

Garner died weeks before Darren Wilson fatally shot Brown in Ferguson, Mo., in early August. In the Missouri case, a grand jury declined to indict Wilson just before Thanksgiving, prompting large, widespread and sometimes chaotic protests, including in New York.

In Ferguson, a section of an outraged crowd followed the grand jury decision with a night of mayhem, damaging two police cars and burning several local businesses to the ground. In a Times Square protest against the Wilson grand jury decision last week, Police Commissioner Bill Bratton was sprayed with a substance resembling blood.

This week, Garner’s family — along with the NYPD, civil rights groups and city officials — expressed hope that demonstrators would greet the decision peacefully. Protesters prepared to assemble ahead of the grand jury decision, Reuters reported.

The city had been preparing for the decision, and any protests or demonstrations it might bring. In a Tuesday news conference, de Blasio said that “the police will act very assertively” if law enforcement officials believe that demonstrations begin to compromise public safety.

Bratton, speaking at the same news conference, said this concerning potential protesters: “Will they engage in some type of demonstration no matter which way the jury goes? Certainly. But I think that there will be an ability — that people will get to have their voices heard without disturbances.”

Likewise, Garner’s 18-year-old son, Eric Snipes, had told the New York Daily News that any response to the grand jury decision in New York is “not going to be a Ferguson-like protest because I think everybody knows my father wasn’t a violent man, and they’re going to respect his memory by remaining peaceful.” He added: “It’s not going to be like it was there.”

[This post has been updated multiple times.]