Derek Chauvin, who knelt on Floyd’s neck, has been charged with second-degree murder, up from third-degree murder.
He also faces a second-degree manslaughter charge. The other three are charged with aiding and abetting second-degree murder and manslaughter.
US President Donald Trump was rebuked by his former defence secretary, James Mattis, who said he was trying to sow divisions.
Trump’s current defence chief, Mark Esper, also said he opposed Trump’s threat to send in the military to quell unrest.
Trump also outraged faith leaders and protesters for walking to a church near the White House for a photo opportunity, minutes after police used chemical smoke canisters and flash-bangs on peaceful protesters to clear the area.
Protesters have remained undeterred by curfews and the presence of the US National Guard in some cities.
Largely peaceful protests have at times turned violent, with looting and vandalism. Wednesday’s protests remained largely peaceful after curfews took effect.
Those protesting against police brutality have been met with, at times, excessive force by authorities.
Journalists have also been targeted by police. Officers have also been injured in the protests.
