Six police officers in Baltimore in the US are facing multiple charges - including second-degree murder, assault and homicide - in connection with the death of Freddie Gray, a black man who died in police custody.
Baltimore City State's Attorney Marilyn Mosby said the death of the 25-year-old Freddie Gray was a homicide, and his arrest was illegal.
Five of the six officers are said to be in custody.
The death of Mr Gray has sparked days of protests and rioting in the east coast port city.
"The findings of our comprehensive, thorough and independent investigation, coupled with the medical examiner's determination that Mr Gray's death was a homicide, which we received today, has led us to believe that we have probable cause to file criminal charges," Ms Mosby told a press conference.
State's Attorney Mosby appeals to #Baltimore people to be peaceful while she seeks justice for Freddie Gray. @rtenews
— Caitriona Perry (@CaitrionaPerry) May 1, 2015State Attorney Mosby, a black woman who is the daughter and granddaughter of police officers, took over the investigation to determine what exactly happened to Mr Gray and whether any of the six officers involved in his arrest should face criminal charges.
Ms Mosby said her office has been conducting its own independent probe.
The US Justice Department is also investigating the case.
A lawyer retained by Baltimore's police union to represent the six officers involved in the case has denounced "an egregious rush to judgement."
"I have never seen such a hurried rush to file criminal charges," declared Michael Davey, a former officer and now a lawyer working for the city's Fraternal Order of Police.
Truth over Freddie Gray's death 'absolutely vital' - Obama
Mr Gray suffered spinal injuries some time between his arrest on 12 April and his arrival at a police station.
Police have said he was not restrained during the ride, a violation of department policies. He died a week later.
US President Barack Obama said it is "absolutely vital" that the truth come out about Mr Gray's death.
"It is absolutely vital that the truth comes out on what happened to Freddie Gray," Mr Obama said at the White House after the dramatic revelation of the charges.
"Justice needs to be served. All the evidence needs to be presented," Mr Obama said, while noting he had not yet seen the specific charges filed and would not comment on the particulars of the case.
"What I think the people of Baltimore want more than anything else is the truth. That's what people around the country expect."
Despite the protests, many questions about Mr Gray's death remain unanswered.
Media reports yesterday provided possible accounts of what may have happened.
Multiple law enforcement sources told local broadcaster WJLA that the medical examiner found Mr Gray's neck appeared to have broken when his head slammed into the back of the van.
He also suffered a head wound matching a bolt jutting from the vehicle's back door, the sources told the station.
The Washington Post cited a prisoner, who rode in the police van with Mr Gray but could not see him, as saying he heard sounds that suggested Mr Gray tried to hurt himself while riding in the vehicle, according to a document written by a police investigator.
Roughly 270 people have been arrested since Monday's violence, and officials have since imposed a citywide 10pm curfew.
Police Commissioner Anthony Batts said on Wednesday more than 100 people had been released without being charged, because officials could not keep up with the paperwork, though he said charges would be brought later.
