NEW YORK (CBSNewYork) — Sources said two officers were injured Tuesday night, as police clashed with demonstrators on the streets of Brooklyn in a protest against police-related deaths and violent incidents throughout the country.

As CBS2’s Valerie Castro reported, the demonstrators started in Union Square and marched down Broadway before targeting the Brooklyn Bridge, 1010 WINS reported. They blocked traffic on the bridge in an effort to bring awareness to what they called police brutality.

Drivers and their passengers were forced to sit and wait, though not all were disappointed.

“I want to go back to Pennsylvania, I want to go back home,” one woman said. “But it’s a good cause, so my hands is up. Please don’t shoot.”

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Protesters took their message to the ground and sat down in the middle of city streets. Officers told them they would be arrested for obstructing traffic.

Early on, several men were taken into custody and led away in handcuffs – in the first of many arrests.

The group eventually made its way to Flatbush Avenue in Brooklyn, and the 78th Precinct police station in Prospect Heights, where more arrests were made.

At one point, police officers tried to move the crowd along with a bullhorn, but that only appeared to anger the group even more, Castro reported.

Pushing and shoving from both protesters and officers led to several arrests. Two officers were allegedly attacked.

Sources told CBS2 one off-duty sergeant was assaulted on the Brooklyn Bridge.

Sources said when his vehicle was blocked by protesters, he got out and a verbal argument ensued with several demonstrators. Then, someone punched him in the face, sources said.

He was taken to NewYork-Presbyterian/Lower Manhattan Hospital with injuries to his face and arm.

A second officer was injured a short time later on Flatbush Avenue in Brooklyn, where he was struck in the head with a bottle, police said.

Some protesters claimed the police officers at the scene used excessive force.

“I got my wrist smashed into,” said Bob Lindgren of Brooklyn. “They threw some guy into a wall.”

“If this shows anything, it’s that police are brutal, and they’re kind of like a gang, and they just take advantage of their power,” added Noelle Tannen of Bedford-Stuyvesant, Brooklyn.

The protesters said the violence Tuesday night was another example of what needs to stop. But Mayor Bill de Blasio said that applies to everyone on both sides.

“Reports this evening that two of our NYPD officers were assaulted by protestors reminds us that here in New York City, violence or threats of violence against the police are unacceptable and will absolutely not be tolerated. These attacks will be thoroughly investigated, and we will urge the full prosecution of the perpetrators,” the mayor said in a statement.

“And any other person who might use the right to peaceful protest as cover to initiate violence, cause mayhem or incite disorder — whether against the police, the people or property of our great City — should consider themselves on notice that New York City will not stand for it. Anyone who decides foolishly to engage in such destructive acts can expect a swift arrest and aggressive prosecution. As I have said before, such activity is beneath the dignity of New York City.”

A total of 22 protesters had been arrested, allegedly for walking in the Brooklyn Bridge roadway or allegedly throwing items from the bridge, police sources told 1010 WINS.

The group organizing the protest calls itself “National Actions to Stop Murder by Police,” and it claimed more than 90 unarmed people have been killed by police in the U.S. since the beginning of the year.

The group says they want to bring awareness to more recent cases of police brutality, including the deadly shooting of an unarmed black man by a white police officer in South Carolina, and to remind people of past cases like the death of Eric Garner, Castro reported.

“This is normal. This is how they think about us. This is how they treat us. They don’t respect the protest, they don’t respect people. This is normal,” said Alex Seel, of Brooklyn.

“Our message is the killer cops have to stop murdering innocent black people all over this country and getting away with it,” Lindgren said.

Protesters said police singled out the group’s organizers early on and made those arrests first, Castro reported.

Late in the evening, the crowd had moved to the 75th Precinct station in East New York, Brooklyn.

Sources said police late Tuesday were still searching for those who attacked the officers.