BOSTON (CBS) -- Tear gas was deployed against protesters in the Downtown Crossing area of Boston around 9 p.m. on Sunday night. By that time, much of the crowd had dispersed.
Thousands had gathered hours earlier in Nubian Square. The protesters were united in their anger over George Floyd's death which sparked unrest across the country.
Around 9:30 p.m., Boston Police tweeted, asking for "peaceful protesters along Tremont Street" to "vacate the area." Dozens of officers were working to clear the area, which had grown hostile.
The National Guard was deployed to the area around 11:15 p.m.
Police said were reports of rocks and bricks being thrown at officers on Tremont Street and "efforts to hurt and harm police officers continue to intensify in our city." A police cruiser was set on fire.
Multiple people were seen being arrested, though the official number of arrests is unclear.
Former Boston Police Commissioner and WBZ-TV Security Analyst Ed Davis said, "It's been in my experience that when you start to make arrests, people start to walk away. Some of the more experienced agitators, the people that are there to cause trouble will actually step up and get arrested because that's what they wanted to do to begin with...but by and large, people don't want to get arrested."
It appeared protesters were also shooting off fireworks, one was seen hitting a police officer.
Davis said, "There is some good news though, in that this is happening after the large crowd has broken up and the fewer people that you have to deal with, the better off you are."
Hours earlier, demonstrators walked through the South End and Chinatown before ending at the State House.
The Boston Police Department asked anyone who was going out to protest to be safe. They tweeted they would be out "in full force to guard and protect everyone's rights. And, while everyone has a right to free speech, nobody has the right to hurt or harm people or property."
Around 6:30 p.m., the crowd was growing by the minute. Thousands chanted "I can't breathe."
"We have to stand up people. This is not a black and white issue anymore. This is humanity. We are all human beings. Aren't you tired of seeing the police brutality? Let's think about it," said Clifton Braithwaite, who was with the crowd.
A group helping to organize the event said they wanted to keep things peaceful.
Nearby restaurant owner Cheryl Straughter said she does not want to see any destruction of property. "I am here as a business owner who is concerned one for Soleil, two for the community, and three for the people who live here and do want to see a protest that's peaceful. We have elders in the community, we have youth in the community so safety is paramount for me," she said.
On Friday, there were 10 arrests during a protest in Boston. On Saturday, the city was mostly quiet while violent protests broke out elsewhere across the country.
"Boston Police has a very good relationship with the community, we've worked really hard to work, neighborhood by neighborhood and to implement community policing and to get out into the neighborhood and talk to people," Davis said. "I think that accounts for sort of the slow burn here, but one of the dynamics is people are watching what's happening around country and they're saying 'we've got to do something' and that something may start off as a peaceful protest but tempers are so high, there's so many conditions that we spoke about that ultimately this happens."
Mayor Marty Walsh thanked peaceful protesters and condemned the violence by tweeting: "I want to thank the protesters who exercised their right to free speech effectively and peacefully…"I am angered, however, by the people who came into our city and chose to engage in acts of destruction and violence, undermining their message."
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