Rage turned to relief in Baltimore Friday when the city’s top prosecutor charged six police officers with felonies ranging from assault to murder in the death of Freddie Gray.

State’s Attorney Marilyn Mosby said Gray’s arrest was illegal and unjustified and that he neck was broken because he was handcuffed, shackled and placed head-first into the back of a police van where his calls for medical attention were repeatedly ignored as he bounced around the van.

The announcement comes less than a day after receiving the police department’s criminal investigation and official autopsy results. Her detailed description of the evidence supporting probably cause to charge all six officers with felonies took some by surprised because of the swiftness of the announcement.

Mosby said the police did not have a reason to stop or chase Gray. They falsely accused him of having an illegal switchblade when in fact it was a legal pocketknife. The van driver and the other officers failed to strap him down with a seatbelt, a direct violation of department policy.

Mosby did not indicate whether there was any indication the driver deliberately drove erratically, causing Gray’s body to strike the van’s interior. In 2005, a man died of a fractured spine after he was transported in a Baltimore police van in handcuffs and without a seatbelt. At a civil trial, an attorney for his family successfully argued police have given him a “rough ride.”

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The officers missed five opportunities to help an injured and falsely imprisoned detainee before he arrived at the police station no longer breathing, Mosby said. Along the way, "Mr. Gray suffered a severe and critical neck injury as a result of being handcuffed, shackled by his feet and unrestrained inside of the BPD wagon," she said.

Mosby’s announcement triggered celebrations across the same Baltimore streets that were engulfed in riots four days later when Gray’s funeral let to major property damage and looting.

Friday night, people were dancing and chanting in the streets to celebrate the charges against the officers. Some people were later arrested by police for defying the citywide curfew that started at 10 p.m. for the fourth straight night.

Earlier in the day, Gray's family urged protesters to remain peaceful while also expressing gratitude for Mosby's decision.

"We are satisfied with today's charges," Gray's stepfather, Richard Shipley, told a news conference. "These charges are an important step in getting justice for Freddie."

But a lawyer hired by the police union insisted the officers did nothing wrong. Attorney Michael Davey said Friday that Mosby has committed "an egregious rush to judgment."

"We have grave concerns about the fairness and integrity of the prosecution of our officers," Davey said.

Mosby rejected a police union request to step aside and appoint a special prosecutor to handle the case, and said honorable police officers should have no problem working with prosecutors in Baltimore.

The six officers turned themselves in at the city jail Friday afternoon after the charges were announced. They were released on bonds of between $250,000 to $350,000 later.

Some law enforcement veterans worried that the charges against the six officers could have a chilling effect. Robert Leight, a former detective in Pennsylvania who has worked for the FBI and as a federal prosecutor and defense attorney, said "the biggest danger is that the police officer will not properly perform his duties."

"It puts him at risk, it puts the other officers around him at risk, and it puts the public at risk," Leight said. "A police officer must react instinctively as he has been trained. If a police officer first thinks about what liabilities he will be facing, it's too late."

Gray was stopped by police in Sandtown, a poor, overwhelmingly African-American neighborhood in West Baltimore. He locked eyes with a police officer and then ran. Two blocks later, they pinned him to the sidewalk, handcuffed him and dragged him into a transport van, a scene captured on bystander's cellphone video and shown around the world.

Mosby said the police review, the autopsy and her own office’s investigation all point to homicide. The officers were booked Friday on charged ranging from assault to manslaughter.

Three officers charged in the case, including the van driver, are also black. The other three are listed as belonging to the broad category of “White, Caucasian, Asiatic Indian Arab,” without further elaboration.

"You have to be able to expect that at some time, the pendulum will swing in your favor, and in the black community we've seen it over and over and over where it doesn't," Otom said. "I'm so happy to see a day where the pendulum has finally begun to swing."

U.S. Rep. Elijah Cummings, a Democrat from West Baltimore, not far from where Gray was raised and arrested, said the neighborhood and others like it "have never seen a victory."

"So many felt like the system had worked against them," Cummings said Friday. "As we approach the evening of our lives, we want to make sure our children have a better morning."

In an impassioned statement delivered shortly after the charges were made public, Mayor Stephanie Rawlings-Blake warned that police misconduct will not be tolerated on her watch.

"To those of you who wish to engage in brutality, misconduct, racism and corruption, let me be clear," she said, "there is no place in the Baltimore City Police Department for you."

Rashawn Ray, a sociologist at the University of Maryland, said the murder and manslaughter charges in Gray's death shape a debate that goes much deeper than legal limits on use of force by police officers. It has triggered the frustration, anger and hopelessness of generations of disenfranchised people in Baltimore's most marginalized neighborhoods, he said.

"This definitely seems like the first time in recent history that the state has done what the community feels is the right thing," Ray said. "These charges become a representation of culpability, responsibility, that the state can't just treat citizens like they are not human beings."

"It's symbolic not just of police brutality," Ray said. "Maybe we are progressing toward the equality that we should have been moving toward decades ago."

The Associated Press contributed to this report