MINNEAPOLIS — On the eve of the criminal trial for Derek Chauvin, the former police officer accused of killing George Floyd and sparking global racial protests, this was a city on edge.

A Sunday afternoon march drew a few thousand people to the Hennepin County Government Center, which these days is encircled by concrete barriers and multiple layers of security fencing. Prince’s “Purple Rain” blared over loudspeakers there, but as the crowd began walking, they did so in silence. They carried a white wooden coffin. Helicopters buzzed overhead.

By then, National Guard vehicles were rolling into the Twin Cities area, delivering the first of more than 3,000 troops expected to be on patrol during what some are calling the biggest trial in Minnesota history.

Chauvin faces second-degree murder and second-degree manslaughter charges as well as a possible third-degree murder charge in connection with the May 25 arrest that ended with Floyd’s death. Chauvin, who is White, was videotaped as he knelt on the neck of Floyd, who was Black, for nearly nine minutes, allegedly asphyxiating him.

Three former officers with Chauvin during the arrest — J. Alexander Kueng, Thomas Lane and Tou Thao — are expected to be tried in late summer. Social distancing and other logistical constraints forced in the courtroom by the coronavirus pandemic are why the four are not being tried together.

Another crowd is anticipated outside the Government Center early Monday, when jury selection is set to start. Opening arguments aren’t expected until the end of the month.

“There’s never been a trial of this magnitude before in these parts,” columnist Rubén Rosario wrote Sunday in the St. Paul Pioneer Press. “Unprecedented. Historic. Momentous. Pick an adjective.”

In a city that saw weeks of civil unrest, injuries and destruction over the summer, tensions quickly rose late Saturday afternoon when a man was fatally shot near the square where the 46-year-old Floyd had died. Police said the shooting appeared to result from an earlier altercation between the victim, whose name has not been released, and the shooter, who remains at large.

People at Sunday’s vigil and march began to gather about 2 p.m. A large black-and-white banner that read “I can’t breathe” was draped on stairs below the simple coffin, on which a spray of red roses had been placed.

Most participants wore black shirts that read, “A man was lynched in Minneapolis on May 25, 2020.”

“I think the primary mood is anger, anger at the killing of George Floyd, anger at the police reaction afterward and anger at the preparations for this trial,” said activist Dave Bicking, a board member of the advocacy group Communities United Against Police Brutality. “And what led to the uprising the first time was anger over the fact that the city has just absolutely avoided doing anything to rein in the police.”

D.A. Bullock, a spokesperson for Reclaim the Block, one of the groups that played a key role in organizing protests immediately after Floyd’s killing, said the extensive fencing and barricades erected around the Government Center and several precincts are a sign of misplaced priorities. City officials spent more than $600,000 on the security measures.

“They’re not protecting any of the buildings around the spaces of the mom-and-pop stores that we lost in north Minneapolis or a lot of the other spaces that ended up being destroyed along Lake Street,” Bullock said. “What has the state been doing all along since last summer to really fortify the people?”

Civil rights attorney and activist Nekima Levy Armstrong read from a 45-foot scroll with more than 400 names of Minnesotans who organizers say have died at the hands of police over the past two decades.

Brandyn Tulloch was struck by how long it took to read. “You just sit and think, ‘Is it always going to be this way?’ When will the police killings end, and when will any of those families ever get justice?” he said.

He isn’t optimistic that Chauvin will be convicted, and he said he doesn’t think that would bring justice anyway. “I feel like it is all eyes on Minneapolis, all eyes on Minnesota. . . . This is because the state is on trial. The system is on trial, and it’s about time they’re held accountable.”

Protests are not limited to Minneapolis right now. About 100 people massed in front of the governor’s mansion in St. Paul, Minn., on Saturday, in part to support nine police overhaul bills they want state lawmakers to pass to increase accountability.

The bills include one that would end qualified immunity as a legal defense for police misconduct, another that would require officers to carry professional liability insurance and a third that would repeal a law that prohibits civilian oversight committees from making findings of fact in police misconduct cases.

“The eyes of the world are going to be on Minneapolis, but our eyes cannot leave the legislature,” said Angela Rose Myers, president of the Minneapolis chapter of the NAACP. “It is our responsibility to make sure the family’s demands are heard.”

The demonstration was led by Families Supporting Families Against Police Violence, an organization made up of relatives of people killed by police.

“All of the mothers, all of us that are walking through the pain of what has been stolen from us,” said Toshira Garraway, whose child’s father, Justin Teigen, died in 2009. “My heart is hurting. I look strong on my outside, but my heart is hurting. I am in a lot of pain.”

The group is also pushing for an additional omnibus bill named for Philando Castile, whom an officer fatally shot in 2016 as he sat in his car in a suburb of St. Paul, his girlfriend beside him and their 4-year-old daughter in the back seat. The officer was acquitted.

“Change is possible,” said Amity Dimock, mother of Kobe Dimock-Heisler, who was killed by police during a mental health crisis in 2019. “We are taking advantage of this possibility.”

Sheila Regan in St. Paul contributed to this report.