NYPD Commissioner William Bratton said Friday that the city should take pride in how largely peaceful the Eric Garner grand jury demonstrations have been this week -- and he expects those protests to "peter out" soon.

"This is what we do in New York. You demonstrate. You have concerns. This is what you do in America," Bratton said, speaking to reporters after his weekly Friday meeting at City Hall with Mayor Bill de Blasio. "I think the city should be feeling quite proud of itself at this juncture. It has a police force that's showing remarkable restraint, and it also has demonstrators who are showing -- most of them -- great restraint."

Bratton said he expects the protests to eventually "peter out" because demonstrators "tend to get tired of marching around aimlessly" and there is rain in the forecast.

So far a small number of protesters have been "overly aggressive" toward police officers and used foul language, he said. Bratton estimated about 10,000 demonstrators marched Thursday night.

Police have been using "selective" arrests rather than mass arrests, so "an individual officer can testify that 'I saw an individual doing this,'" Bratton said.

Mass arrests during the 2004 Republican National Convention cost the city $19 million in settlements, including $7.5 million in lawyers' fees and "phenomenal time" spent on giving depositions, Bratton said of a scenario he did not want to repeat.

Preliminary numbers released by an NYPD official showed 219 people were arrested overnight in the protests, with three people charged with felony reckless endangerment or assault on a police officer.

One person picked up a metal barrier at the Staten Island ferry terminal and threw it at a cop, the official said. Other more minor charges included resisting arrest or obstruction of a government administration, and most of those detained were issued desk-appearance tickets, the official said.

Most of those arrested were New York residents, Bratton said.

Among those arrested in the area of a sit-down at 96th Street was American Federation of Teachers president Randi Weingarten, a law enforcement official said.

A small group of protesters gathered in Union Square on Friday, marking the third day New Yorkers have demonstrated after the grand jury declined to indict NYPD Officer Daniel Pantaleo in the apparent chokehold death of Garner on July 17.

About three dozen people from Brooklyn Preparatory High School chanted "I can't breathe," and "Black lives matter," marching around the square. A light presence of NYPD officers stood watch.

The group then conducted a sit-in at a small park nearby.

Thousands shut down several Manhattan streets on the second night of demonstrations Thursday.

From the heart of the city's governmental core in Foley Square to long strips of the usually bustling West Side Highway, marchers supplanted cars, trucks and city buses as NYPD officers trailed close behind. Some officers were on foot in groups. Others slowly trailed the crowds on motorcycles and in police vehicles. The officers kept their distance, with orange movable barricades at the ready.

The demonstrations in Manhattan and Brooklyn came at the end of a fitful day for the city, marked by de Blasio's praise for the NYPD amid protests Wednesday night, police union attacks on the mayor for his initial emotional comments after the grand jury decision, and the release of details related to the grand jury's decision.

"It's been a really rough week," City Council Speaker Melissa Mark-Viverito told a meeting of progressive leaders Friday morning at City Hall.

"I had hope that we were going to get an indictment," she said of the Garner case, calling justice "elusive."

At the annual Local Progress National Convening meeting, which began Thursday, de Blasio did not expressly mention Garner, but listed the many policy changes underway in the city as a result of grassroots demand. They included a curbing of stop-and-frisks and a municipal ID to be available to immigrants who have arrived in the country illegally.

"It is a burden and a challenge to fight for social change," he said, but it is what is right and what "the people" demand.

De Blasio had struck a wary tone Wednesday night as he talked about the grand jury's decision not to indict Pantaleo. The mayor, the father of two who is married to Chirlane McCray, an African-American, spoke in a halting voice at the news conference about conversations both he and his wife have had with their teenage son, Dante, about avoiding confrontations with police officers.

Leaders of the main NYPD officers union Thursday zeroed in on the mayor's comments the night before. Union president Patrick Lynch said de Blasio "threw New York City officers under the bus" with his remarks on Staten Island.

"While the mayor was behind a microphone, New York City police were out there, protecting people's right to protest in the middle of the night while keeping residents of the city safe," said Lynch, of the Patrolmen's Benevolent Association, which represents the NYPD's rank-and-file officers. "What we need is City Hall to remind citizens we should be afraid of criminals, not police."

De Blasio stood by his earlier comments and said it's hard to deny what is seen on the cellphone video.

"I think people in this city saw a man die who shouldn't have died . . . I think it's important to speak to that reality, particularly when it's not an isolated reality. And if there are critics who don't like that, I would suggest to them that they look more honestly at the reality we're facing and think about the changes we need to make."

De Blasio said change at the NYPD is already starting. He met with Bratton to discuss several developments related to the ongoing investigation into the conduct of officers outside the Staten Island storefront where Garner died.

The mayor said the Garner case would result in the retraining of officers in how to conduct themselves during street encounters with citizens. Bratton said the NYPD is conducting an internal investigation into the officers' conduct.

They will face questioning by the department's internal affairs unit in the company of their lawyers, Bratton said. NYPD officials could not talk with them while they were being investigated by the Staten Island district attorney's office.

Hours after the grand jury decided not to indict Pantaleo under state law, U.S. Attorney General Eric Holder and Brooklyn U.S. Attorney Loretta Lynch announced that a federal investigation is being launched to determine whether Garner's civil rights were violated.

On Staten Island, a judge released bare-bones details Thursday of the grand jury proceedings. The panel sat for nine weeks, heard from 50 witnesses, viewed 60 exhibits, watched four videos and examined medical records and NYPD policies, said state Supreme Court Justice Stephen Rooney.

With John Asbury, Ellen Yan, Nicole Fuller, Gary Dymski, Maria Alvarez, Alison Fox, Dan Rivoli