BALTIMORE — A massive march planned for Saturday to protest the death of a man in police custody is now being billed as a “victory rally” after Baltimore’s top prosecutor filed criminal charges against the six officers involved in the man’s arrest.

The thousands of marchers who are expected to hit the streets this weekend will now do so to celebrate the decision by State’s Attorney Marilyn Mosby to charge the officers with felonies ranging from assault to murder, and encourage continued peaceful demonstrations.

Freddie Gray’s death from spinal injuries a week after his April 12 arrest provoked riots on the streets of West Baltimore on Monday and quickly became a rallying cry against police brutality and social inequality in the city. Mosby’s announcement on Friday triggered celebrations on those same streets.

Mosby said that after reviewing the results of a police investigation turned over to her just one day before, she had concluded Gray’s arrest was illegal and unjustified. She said his neck was broken because he was handcuffed, shackled and placed head-first into a police van, where his pleas for medical attention were repeatedly ignored as he bounced around inside a small metal compartment in the vehicle.

The officers missed five opportunities to help the injured and falsely imprisoned detainee before he arrived at the police station no longer breathing, Mosby added. They even rerouted the van to pick up another passenger, she said.