The charge against former Minnesota police officer Derek Chauvin over the killing of George Floyd has been elevated to second-degree murder, according to a court filing by prosecutors.
The charge is described as meaning Chauvin, who had his knee on Floyd's neck for nearly nine minutes, did the killing unintentionally but "while committing a felony".
The charge could carry up to 40 years in jail.
Meanwhile three additional former police officers have been charged in Floyd's death, court documents show.
Officers Thomas Lane, J Kueng and Tou Thao have been charged with aiding and abetting second-degree murder.
Minnesota Attorney General Keith Ellison is expected to hold a press conference later on Wednesday.
Attorney for Mr Floyd’s family Benjamin Crump released a statement after receiving news of the upgraded charge.
“This is a bittersweet moment. We are deeply gratified that Minnesota Attorney General Keith Ellison took decisive action, arresting & charging ALL the officers involved in George Floyd's death & upgrading the charge against Derek Chauvin to felony second-degree murder,” he shared to Twitter.
Widely seen bystander video showing Mr Floyd's May 25 death has sparked sometimes violent protests in the US and around the world.
Chauvin was fired on May 26 and initially charged with third-degree murder and second-degree manslaughter.
The new charges were filed by Minnesota Attorney General Keith Ellison, who planned an announcement later on Wednesday (local time).
Governor Tim Walz and the Minnesota Department of Human Rights on Tuesday launched a civil rights investigation of the Minneapolis Police Department and its history of racial discrimination, in hopes of forcing widespread change.
The official autopsy by the county medical examiner concluded that Mr Floyd's death was caused by cardiac arrest as police restrained him and compressed his neck.
A separate autopsy concluded he died of asphyxiation due to neck and back compression due to Chauvin's knee on his neck and other responding officers' knees in his back, which made it impossible for him to breathe.
Do you have a story tip? Email: email@example.com.