The white Minneapolis police officer who pressed his knee into George Floyd’s neck was arrested Friday and charged with murder, as authorities imposed overnight curfews to try to stem violent protests over the police killings of African Americans that have spread from Minneapolis and other U.S. cities.

Protesters smashed windows at the CNN headquarters in Atlanta, set a police car on fire and struck officers with bottles. Large protests in New York, Houston and other cities were largely peaceful – even in Minneapolis, where thousands marched downtown as the city's 8 p.m. curfew ticked past and encircled a police precinct station.

"Prosecute the police!" some chanted, and "Say his name: George Floyd!" There was no violence, but some protesters sprayed graffiti on nearby buildings. Elsewhere in the city, forces fired tear gas and rubber bullets to drive back crowds of protesters.

It wasn’t clear if – or how – authorities would enforce the curfew, amid sharp questions about city and state leaders mishandling the crisis. The curfew came the night after protesters burned a police precinct station, and barriers were erected around at least two police precincts before nightfall.

Derek Chauvin, 44, was charged with third-degree murder and second-degree manslaughter. He also was accused of ignoring another officer who expressed concerns about Floyd as he lay handcuffed on the ground, pleading that he could not breathe as Chauvin pressed his knee into his neck. Floyd, who was black, had been arrested on suspicion of using a counterfeit bill at a store.

Chauvin, who was fired along with three other officers who were at the scene, faces more than 12 years in prison if convicted of murder.

An attorney for Floyd’s family welcomed the arrest but said he expected a more serious murder charge and wants the other officers arrested.

Prosecutor Mike Freeman said more charges were possible, but authorities "felt it appropriate to focus on the most dangerous perpetrator."

Meanwhile, Minneapolis Mayor Jacob Frey declared a curfew from 8 p.m. to 6 a.m. Friday and Saturday, with exceptions for emergency responders, the homeless and those seeking medical care.

"I know that whatever hope you feel today is tempered with skepticism and a righteous outrage," Frey said in a statement. "Today’s decision from the County Attorney is an essential first step on a longer road toward justice and healing our city."

Protests also spread across the U.S., fueled by outrage over Floyd’s death and years of police violence against African Americans. Demonstrators clashed with officers in New York and blocked traffic in Houston and San Jose, California. In Atlanta, demonstrators jumped on police cruisers, set one police car ablaze and broke windows at CNN’s headquarters, where hundreds were confronting police.

On Monday, police were trying to put Floyd in a squad car when he stiffened and fell to the ground, saying he was claustrophobic, a criminal complaint said. Chauvin and Officer Tou Thoa arrived and tried several times to get the struggling Floyd into the car.

At one point, Chauvin pulled Floyd out of the car’s passenger side, and Floyd, who was handcuffed, went to the ground face down. Officer J.K. Kueng held Floyd’s back and Officer Thomas Lane held his legs while Chauvin put his knee on Floyd’s head and neck area, the complaint said.

When Lane asked if Floyd should be rolled onto his side, Chauvin said, "No, staying put is where we got him." Lane said he was "worried about excited delirium or whatever."

An autopsy said the combined effects of being restrained, potential intoxicants in Floyd’s system and his underlying health issues, including heart disease, likely contributed to his death. It revealed nothing to support strangulation as the cause of death.

There were no other details about intoxicants, and toxicology results can take weeks. In the 911 call that drew police, the caller describes the man suspected of paying with counterfeit money as "awfully drunk and he’s not in control of himself."

After Floyd apparently stopped breathing, Lane again said he wanted to roll Floyd onto his side. Kueng checked for a pulse and said he could not find one, according to the complaint.

In all, Chauvin had his knee on Floyd's neck for 8 minutes, 46 seconds, including nearly three minutes after Floyd stopped moving and talking, the complaint said.

Chauvin's attorney had no comment when reached by The Associated Press (AP).

The prosecutor highlighted the "extraordinary speed" in charging the case just four days after Floyd’s death and defended himself against questions about why it did not happen sooner. Freeman said his office needed time to gather evidence, including what he called the "horrible" video recorded by a bystander.

It was not immediately clear whether Chauvin's arrest would quiet the unrest, which escalated again Thursday night as demonstrators burned a Minneapolis police station soon after officers abandoned it.

News of the arrest came moments after Minnesota Gov. Tim Walz acknowledged the "abject failure" of the response to the protests and called for swift justice for the officers. Walz said the state had taken over the response to the violence.

"Minneapolis and St. Paul are on fire. The fire is still smoldering in our streets. The ashes are symbolic of decades and generations of pain, of anguish unheard," Walz said. "Now generations of pain is manifesting itself in front of the world – and the world is watching."

President Donald Trump threatened action, tweeting "when the looting starts, the shooting starts," which prompted a warning from Twitter for "glorifying violence." Trump later said he was referring to the shooting that had happened during the protests.

Later, the president said he'd spoken to Floyd’s family and "expressed my sorrow."

Trump called the video of the arrest "just a horrible thing to witness and to watch. It certainly looked like there was no excuse for it."

The governor faced tough questions about the National Guard's slow response, saying city leaders were in charge. But Walz said it became apparent as the 3rd Precinct station burned Thursday night that the state had to step in.

"You will not see that tonight, there will be no lack of leadership," Walz said Friday.

A visibly tired and frustrated Frey, the Minneapolis mayor, took responsibility for evacuating the police precinct, saying it had become too dangerous for officers.

Nearly every building in a shopping district a couple of blocks from the abandoned police station had been vandalized, burned or looted. National Guard members carrying assault rifles lined up at some intersections, keeping people away from the police station. Dozens of volunteers swept up broken glass in the street.

Dean Hanson, 64, who lives in a nearby subsidized housing apartment, said his building lost electricity overnight. Residents were terrified as they watched mobs loot and burn their way through the neighborhood, he said.

"I can’t believe this is happening here," Hanson said. "It was pure hell."

Dozens of fires were also set in St. Paul, where nearly 200 businesses were damaged or looted.

Attorney Benjamin Crump, who is representing Floyd's family, asked to take custody of Floyd's body for an independent autopsy.

The doctor who will do the autopsy is Michael Baden, former chief medical examiner of New York City, who was hired to do an autopsy for Eric Garner, a black man who died in 2014 after New York police placed him in a chokehold and he pleaded that he could not breathe.

State and federal authorities also are investigating Floyd's death.

The owner of a popular Latin nightclub said Floyd and Chauvin both worked as security guards there as recently as last year, but it’s not clear whether they worked together. Chauvin served as an off-duty security guard at the El Nuevo Rodeo club for nearly two decades, and Floyd had worked there more recently for about a dozen events featuring African American music, Maya Santamaria told the AP.

Santamaria, who recently sold the venue, said Chauvin got along well with the regular Latino customers but did not like to work the African American nights. When he did, and there was a fight, he would spray people with mace and call for police backup and half-dozen squad cars would soon show up, something she felt was "overkill."