President Joe Biden said the verdict "can be a giant step forward" in the fight against systemic racism in America but stressed that "it's not enough".
Former Officer Derek Chauvin was convicted of third-degree murder and manslaughter on Tuesday over the death of George Floyd, a black man who Chauvin pinned to the pavement in May of last year with a knee on his neck.
The case set off a furious reexamination of racism and policing in the US.
The verdict arrived after about 10 hours of deliberations over two days.
It was read late in the afternoon in a city on edge against the possibility of more unrest after violent protests erupted last spring.
Chauvin was convicted of all three charges of third-degree murder, second-degree unintentional murder, and second-degree manslaughter.
His face was obscured by a COVID-19 mask, and little reaction could be seen beyond his eyes darting around the courtroom. His bail was immediately revoked and he was led away with his hands cuffed behind his back.
Sentencing will be in two months.
A city on edge
When the final guilty verdict was announced, a crowd outside the courtroom roared with many people hugging and some shedding tears.
At the intersection where Floyd was pinned down, another crowd chanted, "One down, three to go!,'' in a reference to the three other fired Minneapolis police officers facing trial in August on charges of aiding and abetting murder in Floyd's death.
The courthouse was ringed with concrete barriers and razor wire, and thousands of National Guard troops and law enforcement officers were brought in ahead of the verdict. Some businesses boarded up with plywood.
Floyd died last May after Chauvin, a 45-year-old now-fired white officer, pinned his knee on or close to the 46-year-old black man’s neck for about 9 1/2 minutes as Floyd gasped that he couldn't breathe and onlookers yelled at Chauvin to stop.
The jury was made up of six white people and six Black or multiracial people.
The city has been on edge in recent days — not just over the Chauvin case but over the deadly police shooting of a 20-year-old Black man, Daunte Wright, in the nearby Minneapolis suburb of Brooklyn Center on April 11.
'A giant step forward'
President Joe Biden said the verdict "can be a giant step forward" in the fight against systemic racism in America but stressed that "it's not enough"
"'I can’t breathe.' Those were George Floyd’s last words," Biden said from the White House. "We can’t let those words die with him. We have to keep hearing those words. We must not turn away. We can’t turn away."
Kamala Harris, the first Black woman to serve as vice president, said racism was keeping the country from fulfilling its founding promise of "liberty and justice for all."
"It is not just a Black America problem or a people of colour problem. It is a problem for every American," she said. "It is holding our nation back from reaching our full potential."
"A measure of justice isn’t the same as equal justice," she said.
Biden and Harris called on Congress to act swiftly to address policing reform, including by approving a bill named for Floyd, who died with his neck under Chauvin’s knee last May. Beyond that, the president said, the entire country must confront hatred to “change hearts and minds as well as laws and policies.”
Their joint address comes after Biden said he had spoken to Floyd’s family on Monday and “can only imagine the pressure and anxiety they’re feeling.”
“They’re a good family and they’re calling for peace and tranquility no matter what that verdict is,” Biden said. “I’m praying the verdict is the right verdict. I think it’s overwhelming, in my view. I wouldn’t say that unless the jury was sequestered now.”
The president has repeatedly denounced Floyd’s death but previously stopped short of commenting on the trial itself.
'A catalyst' for reform
The Congressional Black Caucus watched the verdict together in the Capitol, and members hugged and fist-pumped after the verdict was read.
Ohio Rep. Joyce Beatty, welcomed the verdict and said in a statement: "I am hopeful that today will be the catalyst to turn agony into action because the American people are demanding transparency, accountability, and equal justice. Congress should listen too and pass the George Floyd Justice in Policing Act."
House Speaker Nancy Pelosi also called for the George Floyd Justice in Policy Act to be enacted into law.
"George Floyd should be alive today. His family's calls for justice for his murder were heard around the world. We must make sure that other families don't suffer the same racism, violence and pain," she wrote on Twitter.
The Black Lives Matter advocacy group welcomed the ruling but deplored it took "330 days to confirm what we already knew."
"This isn't proof the system works. It's proof of how broken it is. Because it took us this long, and this much attention. Until we live in a world where our communities can thrive free from fear, there will be justice," it added.