New charges have been announced against all of the sacked police officers present at the death of African American George Floyd in Minneapolis.
The charge against Derek Chauvin has been elevated to second-degree murder, court documents show.
The other three officers, previously uncharged, face counts of aiding and abetting murder.
Floyd’s death has sparked huge protests across the US against racism and the police killings of black Americans.
The vast majority of demonstrations over the past eight days have been peaceful, but some have turned violent and curfews have been imposed in a number of cities.
Announcing the new charges, Minnesota’s Attorney General Keith Ellison said that they were in the interests of justice.
Derek Chauvin had initially faced charges of third-degree murder and second-degree manslaughter. These will stay on his charge sheet.
The other three sacked officers are Thomas Lane, J Alexander Kueng and Tou Thao. They all face charges of aiding and abetting second-degree murder, and aiding and abetting second-degree manslaughter.
Minnesota Senator Amy Klobuchar said on Twitter that the latest charges were “another important step for justice”.