MINNEAPOLIS -- London Williams stood in Black Lives Matter Plaza in Washington, D.C., moments before the verdict was read in George Floyd's murder trial Tuesday, wondering how he would cope if the white police officer who killed the Black man was acquitted.

"I feel very nervous. It's already hard as it is as a Black man in today's society," said Williams, standing with a date in the space near the White House renamed after Floyd's death last May. "If this doesn't go right, I don't know how safe I will feel."

Then, the verdict came for former Minneapolis Officer Derek Chauvin: guilty on all counts. Williams, 31, doubled over with emotion, covered his face and wept.

With that outcome, Black Americans from Missouri to Florida to Minnesota cheered, marched, hugged, waved signs and sang jubilantly in the streets. The joy and relief stood in stark contrast to the anger and sometimes violent protests that engulfed the country following Floyd's death.

But Tuesday's celebrations were tempered with the heavy knowledge that Chauvin's conviction was just a first step on the long road to address racial injustices by police.

Many said they had prepared for a different result after watching countless deaths of people of colour at the hands of police who went unpunished. The shooting death of another Black man, Daunte Wright, by officers in suburban Minneapolis during the trial and of 13-year-old Adam Toledo in Chicago last month heightened tensions and muted the court victory for many.

In Columbus, Ohio, some residents had their celebration over the verdict cut short by reports that police fatally shot a teenage Black girl. "As you're getting one phone call that he was guilty, I'm getting the next phone call that this is happening in my neighbourhood," Kimberly Shepherd said. Several hours later, police released body-camera footage that appeared to show the officer firing just as the girl lunged at another female with a knife.

The Rev. Jesse Jackson travelled to Minneapolis for the verdict, and said there was relief but no celebrating "because the killing continues."

"Finally we did get some justice," Gwen Carr, the mother of Eric Garner, a Black man who died at the hands of police in New York City in 2014, said after pronouncing herself "elated" at the verdict. No criminal charges were brought in her son's death; his last words were "I can't breathe," which became a rallying cry among activists.

In St. Louis, a police association of about 260 predominantly Black officers called the verdict important but "a pebble in the ocean."

"Yet, why should we be thankful for something that is right? Why should we be thankful when George Floyd doesn't have his life or his future?" the Ethical Society of Police said in a statement.

Many saw the trial as a litmus test for how sincere Americans are about racial justice and consequential police reform after Floyd's death set off global protests. Jurors in the high-profile case deliberated for 10 hours over two days. Chauvin was handcuffed and taken into custody immediately after the verdict was read.

"It means so much to me," said Venisha Johnson, a Black woman who cried at a gathering in what's been dubbed George Floyd Square in Minneapolis. "I've been praying for George every day, every morning at 6 a.m. I'm just so happy. The way he was murdered was terrible! But thank you, Jesus."

In Los Angeles, several dozen people gathered to celebrate at the corner of Florence and Normandie avenues, which was the scene of chaos and violence in 1992 when the city dissolved into riots after four officers were acquitted in the beating of motorist Rodney king. A Black man in a Lakers cap danced and chanted: "Get used to this, get used to justice!" Passing cars blared their horns as demonstrators waved signs and Black Lives Matter flags.

In Houston's Third Ward, the historically Black neighbourhood where Floyd grew up, a small crowd gathered under a tent near a mural of Floyd to listen as the verdict was read on TV. People driving by honked their car horns and yelled, "Justice!"

"We feeling good. We thank everybody that stood with us. It's a blessed moment," said Jacob David, 39, who knew Floyd and wiped away tears.

Floyd's death on May 25, 2020, as Chauvin pressed a knee to his neck and the graphic bystander video that captured him pleading that he couldn't breathe shocked and appalled the world and triggered protests against police brutality and racial injustice.

"We've just become so accustomed to not receiving justice. I'm just so very, very overwhelmed right now," said Tesia Lisbon, a community activist in Florida's capital of Tallahassee.

Lisbon was one of 19 people arrested by police last September during a Black Lives Matter march.

"We just got so used to not hearing good news, to not having the justice system on your side for so long," Lisbon said.

Law enforcement in many cities had prepared for unrest.

In Grand Rapids, which had some of Michigan's worst violence after Floyd's death, authorities placed concrete barriers around the police building before the verdict was announced. Officials said they would protect the right to peacefully assemble but also wanted to be on guard for "chaos and destruction."

Michigan Gov. Gretchen Whitmer called Tuesday's verdict "a reminder to continue pushing for justice in every corner of our society."

And in Portland, Oregon, which has seen repeated protests and vandalism since Floyd's death, the mayor declared a state of emergency and put state police and the National Guard on standby. Small groups of protesters have set fires, broken windows and vandalized buildings, including a church, a Boys & Girls Club and a historical society in recent days over the deaths of Wright and Toledo, as well as a fatal police shooting in Portland last week.

In overwhelmingly white Vashon Island off Seattle, resident Karen Oneil watched the verdict with her handmade sign half painted. One side said, "Justice For George." She didn't know what to write on the other -- a message of relief or of protest -- until the verdict came down.

When she headed to the island's quaint downtown to wave it, the white paint reading "Hope Begins" was still wet.

"People can celebrate today, but there is a lot of work to be done," Oneil said.

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Morrison reported from Minneapolis; Flaccus from Portland, Oregon; and Martin from Washington. Associated Press writers Sophia Tareen in Chicago; Bobby Caina Calvan in Tallahassee, Florida; Juan Lozano in Houston; Jim Salter in St. Louis; Stefanie Dazio in Los Angeles and Gene Johnson in Vashon Island, Washington, contributed to this report.