Maryland State Attorney Marilyn Mosby has filed criminal charges against six officers in the case of Freddie Gray who died in police custody on April 19.

The state prosecutor said the death of the 25-year-old black man was a homicide, and his arrest was illegal.

Protesters cheered as Marilyn Mosby announced charges ranging from second-degree murder to assault. But a lawyer for the officers says they “did nothing wrong”.

Freddie Gray’s death – from injuries in custody – sparked protests that turned violent.

Marilyn Mosby said at a news conference: “The findings of our comprehensive, thorough, and independent investigation coupled with the medical examiner’s determination was a homicide… has led us to believe that we have probable cause to file criminal charges.”

Celebrations broke out across Baltimore after the announcement. Drivers honked their car horns as people took to the streets with fists raised in triumph.

Marilyn Mosby said Freddie Gray died as a result of injuries suffered while he was shackled inside a Baltimore police van, but not restrained by a seat belt – as he was legally required to be.

She said the officers failed to provided medical aid to Freddie Gray after he repeatedly pleaded for help.

Baltimore Mayor Stephanie Rawlings Blake said that five of the officers were in custody. The sixth later turned himself in. The officers were suspended after Freddie Gray’s death.

“No one in our city is above the law,” Stephanie Rawlings Blake said.

“Justice must apply to all of us equally.”

The driver of the van, Caesar Goodson, 45, faces the most serious charge, second-degree murder.

Caesar Goodson faces more than 30 years in prison if convicted.

The other officers face charges including involuntary manslaughter, assault and misconduct.

“To the people of Baltimore and the demonstrators across America, I heard your call for <<no justice, no peace>>. Your peace is sincerely needed, as I work to deliver justice on behalf of this young man,” Marilyn Mosby said.

Marilyn Mosby said that Freddie Gray was not carrying a switchblade as reported earlier by police, but a legal pocketknife.

The police union defended the officers and said they acted “diligently”. The union called for an independent prosecutor, something Marilyn Mosby said was not needed.