Protesters clashed with riot police who used teargas in an effort to disperse crowds as businesses in downtown Minneapolis were burned and vandalized.

The violence erupted two days after a video showing former Minneapolis Police Officer Derek Chauvin kneeling on Floyd’s neck during an arrest that resulted in the latter’s death—and hours after Minneapolis Mayor Jacob Frey called for Hennepin County Attorney Mike Freeman to file criminal charges against Chauvin.

“I have wrestled with—more than anything else over the last 36 hours— one fundamental question: Why is the man who killed George Floyd not in jail,” Frey said to reporters on Wednesday. “If you had done it or I had done it, we would be behind bars right now. George Floyd deserves justice. His family deserves justice, the black community deserves justice, and our city deserves justice.”

On Wednesday night, thousands of protesters wearing face coverings surrounded the MPD’s Third Precinct police station, about half a mile from where Floyd had been arrested, according to a Reuters report.

Police officers formed a human barricade around the precinct and confronted protesters who chanted “No justice, no peace” and “I can’t breathe.”

Floyd, 46, was accused of passing a counterfeit $20 at the Cup Foods on Monday. He was taken into custody outside the store and did not resist arrest, according to video evidence recorded by a bystander.

Video of police officer Chauvin kneeling on a prone and handcuffed Floyd—who was repeatedly heard on the video telling officers “I can’t breathe”—went viral.

Chauvin and three other police officers involved in the arrest were fired.

On Thursday, the Department of Justice Civil Rights Division, the U.S. Attorney’s Office in Minnesota, and the FBI’s Minneapolis field office announced in a joint statement that they were conducting a “robust investigation” into the actions leading up to Floyd’s death in order to determine if police violated Floyd’s civil rights. If proven, it may result in federal charges against Chauvin and the other officers involved.

It is a violation of federal law for an individual acting under color of law to willfully deprive another person of any right protected by the Constitution or laws of the United States, according to the DOJ.

“The Department of Justice has made the investigation a top priority and has assigned experienced prosecutors and FBI criminal investigators to the matter,” the statement read.