MINNEAPOLIS, United States (AP) — Violent protests over the death of a black man in police custody rocked a Minneapolis neighbourhood for a second-straight night as angry crowds looted stores, set fires and left a path of damage that stretched for miles. The mayor asked the governor to activate the National Guard.

The protests that began late Wednesday and stretched into yesterday morning were the most destructive yet since the death of George Floyd, who was seen on video gasping for breath during an arrest in which an officer kneeled on his neck for almost eight minutes. In the footage, George pleads that he cannot breathe and slowly stops talking and moving.

Mayor Jacob Frey sought calm. “Please, Minneapolis, we cannot let tragedy beget more tragedy,” he said on Twitter.

Protests also spread to other US cities. In California, hundreds of people protesting Floyd’s death blocked a Los Angeles freeway and shattered windows of California Highway Patrol cruisers. Memphis police blocked a main thoroughfare after a racially mixed group of protesters gathered outside a police precinct. The situation intensified later in the night, with police donning riot gear and protesters standing shoulder-to-shoulder in front of officers stationed behind a barricade.

Minneapolis police said the violence contrasted sharply with a mostly peaceful demonstration Tuesday afternoon at the street corner where Floyd died.

“They were chanting for things to remain peaceful,” police spokesman John Elder said. “Tonight didn’t have the same feel. And that’s sad.”

Pockets of looting continued yesterday. A liquor store employee displayed a gun as he stood among the debris of broken bottles and beer cans inside the business.

Amid the violence, a man was found fatally shot Wednesday night near a pawn shop, possibly by the owner, authorities said.

Fire crews responded to about 30 intentionally set blazes during the protests, including at least 16 structure fires, and multiple fire trucks were damaged by rocks and other projectiles, the fire department said. No one was hurt by the blazes.

Firefighters were still spraying water onto hot buildings yesterday morning, and some buildings still smouldered, sending a bitter smell into the smoke-filled air.

Windows were smashed out of several businesses in a strip mall, including a department store, a charter school and other businesses, and the destruction was visible for blocks. A Wendy’s restaurant was damaged beyond recognition.

Inside some of the stores, shelves were toppled and debris strewn about. Video taken inside a damaged Target that had been looted showed empty clothing racks. Obscenities were spray-painted on the outside of the store. Streets and parking lots were also covered in debris, and many businesses had been spray-painted.

There was no sign of a police presence, except around the precinct building, where officers were in riot gear. One man standing outside the building was using a bullhorn to shout. “I can’t breathe, I can’t breathe. Mama, I can’t breathe,” repeating some of Floyd’s pleas for relief.

Across from the precinct, someone had spray-painted the side walk in red: “Where’s humanity?”

Protesters began gathering Wednesday afternoon near the city’s third precinct station, in the southern part of the city, where the 46-year-old Floyd died on Memorial Day as police arrested him outside a convenience store on a report of a counterfeit bill being passed. Demonstrators also skirmished with officers, who fired rubber bullets and tear gas in a repeat of Tuesday night’s confrontation.

The US Attorney’s Office and the Federal Bureau of Investigations (FBI) in Minneapolis said yesterday they were conducting “a robust criminal investigation” into Floyd’s death and making the case a priority. The announcement came a day after President Donald Trump tweeted that he had asked an investigation to be expedited.

The FBI had already announced that it would investigate whether Floyd’s civil rights were violated.

The officer who kneeled on Floyd and three others were fired Tuesday. On Wednesday, the mayor called for him to be criminally charged.

Frey appealed to Governor Tim Walz to activate the National Guard, a spokesman confirmed yesterday. The governor’s office did not immediately respond to a request for comment. Walz tweeted for calm Wednesday night, calling the violence “an extremely dangerous situation” and urging people to leave the scene.

The last time the Minnesota National Guard was called out to deal with civil unrest was in a backup role during the 2008 Republican National Convention in St Paul. The most comparable situation to the current disturbances happened when the Guard was called up to deal with the riots in Minneapolis in 1967, a summer when anger over racial inequalities came to a boil in many cities across the country.

The Minnesota National Guard was also called out during protests against the Vietnam War in the 1960s and early 1970s and during a 1986 strike by Hormel meat packers in Austin.