The verdict was read by the judge just after 5 p.m.
Chauvin was facing three counts -- second-degree unintentional murder, third-degree murder and second-degree manslaughter.
Leaders from Black Lives Matter Greater NY broke the news to a crowd that had assembled in Union Square. As CBS2's Aundrea Cline-Thomas reports, the crowd erupted into cheers and cars passing by started honking.
They told the crowd the conviction came about because of the relentless protests and pressure of everyday people who would not give up.
For many, last summer may have been the first time they hit the streets in protest, but activists say they've been pounding the pavement for years. They compared this case to Eric Garner's death saying, in their words, this time finally feels like justice.
"I feel the American system gave the people justice. I was on the ground when they announced they were going to arrest Chauvin, in George Floyd Square. I've been beaten for George Floyd. We've gone to jail for George Floyd. But today I can rejoice. I can smile and know that this can be a government that is for and by the people," said Chivona Newsome, with Black Lives Matter Greater NY.
While there's a sigh of relief among those who were hoping for this verdict, Newsome says there is more work to be done and while Floyd's murder represented longstanding concerns about policing, especially in Black and brown communities, they say efforts for reform are far from over.
Hundreds gathered at the Barclays Center in Brooklyn before marching along Flatbush Avenue, chanting George Floyd's name.
Some told CBS2's Ali Bauman they feel vindicated, but the overwhelming tone was a melancholy relief. Protesters were glad for the guilty verdict, but for many, it's just one step in a very long journey.
"I wanted to cry. I literally wanted to cry," Brooklyn resident Shamyia Brown said. "These are our families. These are our brothers. I imagine my father."
"I hope it's the beginning of something that leads to a re-evaluation of the system and change," Greenpoint resident Don Brody said.
Many of those marching Tuesday night had been protesting in the same are last summer. While the tone is different this time, the message is still the same.
"It's such a contrast. I was here around this time last year for the same topic, and it's a stark contrast right now," Brody said.
"It's a victory. It's a step in the right direction. Lot more steps we have to take. We will continue to march until the laws are changed," Brooklyn resident, James McEougal said.
"It's hard for me to be celebratory because I know how much work is left and what needs to be done," Public Advocate Jumaane Williams said.
"We're all together in this. It's not just one. It's all of us," Brooklyn resident Duwayne Carthan said.
Demonstrators gathered in Times Square hours after Chauvin's conviction.
"This is only happening as a result of mass struggle," Bronx resident Sasha Murphy said.
"This was a victory won for and by the people," Monica Cruz, of West New York, New Jersey, said.
The historic verdict filled the eyes of Sammy Feliz with tears, remind him of his brother, Alan Feliz, who was shot and killed by police nearly two years ago.
NYPD investigators said they believed Alan Feliz was trying to run over an officer during a traffic stop in the Bronx.
"Seeing your loved one being brutally murdered, it takes a lot from you. You lose a piece of yourself," Sammy Feliz told CBS2's Cory James. "So now I'm living through him."
Many people are living through similar cases.
It's why demonstrators rallied on Long Island and a large crowd came together in Harlem.
New Yorkers all over plan to continue to speak out because they feel this is their moment of hope, and they are fighting to keep it from being their last.
"This is our verdict," Murphy said.
"This fight is not over," Cruz said.
"The reality is that it could be another person tomorrow," said Isaiah Fenichel, an organizer for Strategy for Black Lives.
Earlier, NYPD Commissioner Dermot Shea tweeted, "Justice has been served. NYPD will be out tonight to ensure that peaceful demonstrations have the ability to proceed safely."
The NYPD says they were prepared for protests and had executed their mobilization plan with specialized units like the strategic response group and the critical response command.
There have been no protest-related arrests.
More protests are expected to happen in Manhattan throughout the week.
CBS2's Aundrea Cline-Thomas, Ali Bauman and Cory James contributed to this report.
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