MINNEAPOLIS (AP) — The police officer who was seen on video kneeling on the neck of George Floyd, a handcuffed black man who died in custody after pleading that he could not breathe, was arrested Friday and charged with murder in a case that sparked protests across the United States and violence in Minneapolis.

Hennepin County Attorney Mike Freeman said Derek Chauvin was charged with third-degree murder and manslaughter. Freeman did not provide immediate details, but said a criminal complaint would be made available later Friday and that more charges were possible.

In the video, Chauvin is seen kneeling on Floyd’s neck as Floyd is on the ground. He gradually becomes motionless as Chauvin and three other officers ignore bystanders’ shouts to get off him. Freeman said the investigation continues into the other three officers, but that authorities “felt it appropriate to focus on the most dangerous perpetrator.”

Freeman highlighted the “extraordinary speed” in charging the case just four days after Floyd’s death, but also defended himself against questions about why it did not happen sooner. He said his office needed time to put evidence, including what he called the “horrible” video by a bystander. He said he would not bring a case unless he had enough evidence to prove the charges beyond a reasonable doubt.

Protests in Minneapolis escalated in violence on Thursday, when demonstrators torched a police station that officers had abandoned.

“I’m not insensitive to what happened in the streets,” Freeman said. “My own home has been picketed regularly.”

All four officers who were at the scene of Floyd’s death were fired the next day. After the charges were announced, protesters outside the government center chanted, “All four got to go.”

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 officers involved. Walz said the state would take over the response to the violence and that it’s time to show respect and dignity to those who are suffering.

“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, adding. “Now generations of pain is manifesting itself in front of the world — and the world is watching.”

The governor cited a call he received from a state senator who described her district “on fire, no police, no firefighters, no social control, constituents locked in houses wondering what they were going to do. That is an abject failure that cannot happen.”

His comments came the morning after protesters torched a police station that officers abandoned during a third night of violence. Livestream video showed protesters entering the building, where intentionally set fires activated smoke alarms and sprinklers. President Donald Trump threatened action, tweeting “when the looting starts, the shooting starts,” which prompted a warning from Twitter for “glorifying violence.”

The governor faced tough questions after National Guard leader Maj. Gen. Jon Jensen blamed a lack of clarity about the Guard’s mission for a slow response. Walz said the state was in a supporting role and that it was up to city leaders to run the situation. Walz said it became apparent as the 3rd Precinct was lost that the state had to step in, which happened at 12:05 a.m. Requests from the cities for resources “never came,” he said.

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

On Friday morning, nearly every building in the shopping district around the abandoned police station had been vandalized, burned or looted. National Guard members were in the area, with several of them lined up, keeping people away from the police station.

Dozens of volunteers swept up broken glass in the street, doing what they could to help.

Dean Hanson, 64, lives in a subsidized housing unit nearby, which is home to many older residents. He said his building lost electricity overnight, and residents were terrified as they watched mobs of people run around their neighborhood, with no apparent intervention.

“I can’t believe this is happening here,” he said.

Dozens of fires were also set in nearby St. Paul, where nearly 200 businesses were damaged or looted. Protests spread across the U.S., fueled by outrage over Floyd’s death, and years of violence against African Americans at the hands of police. Demonstrators clashed with officers in New York and blocked traffic in Columbus, Ohio, and Denver.

Trump threatened to bring Minneapolis “under control,” calling the protesters “thugs” and tweeting that “when the looting starts, the shooting starts.” The tweet drew another warning from Twitter, which said the comment violated the platform’s rules, but the company did not remove it.