Hundreds of troops deployed to the streets of Minneapolis and St. Paul early Friday after the third night of rioting over police brutality against African Americans left hundreds of shops damaged and a police station on fire.
After the angry demonstrations spread overnight to multiple US cities, from New York to Phoenix, President Donald Trump blasted local officials and labelled the protestors "thugs" and threatened a harsh crackdown.
Black leaders continued to express outrage over the videotaped death of George Floyd, 46, while handcuffed on the ground and in custody of Minneapolis police on Monday. He died after one officer kneeled on his neck for more than five minutes.
"People are angry they are frustrated because this is not the first police killing they have seen around the country," Al Sharpton, a prominent black rights activist, told MSNBC.
Trump indicated he would counter more street violence with more troops on the streets.
"These THUGS are dishonouring the memory of George Floyd, and I won't let that happen," Trump tweeted.
"Just spoke to (Minnesota) Governor Tim Walz and told him that the Military is with him all the way. Any difficulty and we will assume control but, when the looting starts, the shooting starts."
Twitter concealed that tweet, saying it violated its policy on glorifying violence.
Overnight demonstrators broke through law enforcement barriers to overtake the Minneapolis police station where the four officers blamed for Floyd's death were based.
A fire broke out and soon became an inferno that engulfed the structure.
The state's national guard announced the 500 troops were being deployed Friday morning for peacekeeping amid signs that the anger was nowhere near dissipating.
"Our troops are trained to protect life, preserve property and ensure people's right to peacefully demonstrate," said Major General Jon Jensen of the Minnesota National Guard.
Protests broke out in several cities across the country, including New York, where dozens of protestors were arrested; Phoenix, Memphis, and Denver.
In Louisville, Kentucky, seven people were hit by gunfire at a protest on Thursday over the death of Breonna Taylor -- a black woman who was shot after police entered her home in March.
One of those wounded was in critical condition, according to the Louisville Metro Police Department. It is not yet clear who fired the shots.
Police urged protestors to "please choose peace," posting a video message from a member of Taylor's family asking those in the streets to "go home and be safe and be ready to keep fighting."
But more protests were expected Friday, including in Washington and Houston, where Floyd's family is.
Pressure mounted on Minnesota officials to arrest the four officers blamed for Floyd's death.
A video shows that after being detained on a minor, non-violent charge of using a counterfeit banknote, he was handcuffed, pinned to the ground and one officer held his knee tightly to Floyd's neck for more than five minutes until he went limp.
Floyd's family demanded the officer be arrested for murder, but local and federal law enforcement officials said Thursday they still needed to investigate the case thoroughly.
"The Department of Justice has made the investigation in this case a top priority," said Erica MacDonald, the US federal attorney for Minnesota.
"To be clear, President (Donald) Trump, as well as Attorney General William Barr, are directly and actively monitoring the investigation in this case."
But Sharpton said Friday that video of Floyd's death was strong enough to support arresting the officers, who have been fired from the Minneapolis police.
"The tape is more than enough to establish probable cause .. to make an arrest. There is no reason these four policeman have not been arrested by now."