BALTIMORE (AP) - Saying "no one is above the law," Baltimore's top prosecutor announced charges Friday against six officers involved in the arrest of a black man whose neck was broken in police custody, a decision that comes amid outrage around the country over police brutality against African-Americans.

State's Attorney Marilyn Mosby declared that Freddie Gray's death was a homicide, his arrest was illegal, and his treatment amounted to murder and manslaughter. She detailed what happened to Gray during his arrest and the more than 30-minute ride in a police wagon, her outline either contradicting what police have said or shedding far more light on what happened inside the wagon.

Gray's knife was legal, not illegal as an officer claimed. And officers repeatedly refused to get Gray medical help, even though he kept asking for it, telling them he needed an inhaler and later that he couldn't breathe. At one point, he was shackled at the legs and put back in the wagon on his stomach. At another stop, an officer "spoke to the back of Mr. Gray's head," and even though he was unresponsive, made "no effort to look or assess or determine his condition."

"The findings of our comprehensive, thorough and independent investigation, coupled with the medical examiner's determination that Mr. Gray's death was a homicide," Mosby said, "has led us to believe that we have probable cause to file criminal charges."

Onlookers cheered and expressed amazement over Mosby's announcement, which few expected so quickly. The city, which saw looting and businesses and cars burned on Monday, was still under a nighttime curfew and National Guard troops and police were out in full force. More than 200 people have been arrested and police said nearly 100 officers were injured.

As Mosby spokes on the steps of the War Memorial Building, cheers and shouts of "Justice!" erupted. Mosby announced the charges one day after receiving the results of the internal police investigation and the autopsy report. As she spoke, the city braced for huge protests Friday and Saturday.

"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.

The stiffest charge -- second-degree "depraved heart" murder -- was filed against driver of the police van. The other five were charged with crimes including manslaughter, assault, false imprisonment and misconduct in office.

Fraternal Order of Police local president Gene Ryan told Mosby in a letter before the charges were announced Friday that none of the six suspended officers were responsible for Gray's death. Attorney Michael Davey, who is representing at least one of the officers, is expected to hold a news conference Friday afternoon.

It's not clear who is representing the other officers. They have not returned telephoned messages.

President Barack Obama said it was "absolutely vital that the truth comes out." He said he doesn't comment on the legal process, "but I can tell you that justice needs to be served."

"Those individuals who are charged obviously are also entitled to due process and rule of law," he said.

Mosby said Gray was illegally arrested and assaulted. He was handcuffed and then hoisted into the metal compartment of a police van without the seatbelt that all officers are told they must put on for safety of both detainees and officers. The van's driver failed to restrain Gray at least five different times, she said.

At some point along the way, Gray suffered a mysterious spinal injury and died a week later.

Mosby said what police described as an illegal switchblade - Officer Garrett E. Miller swore in a court record under penalty of perjury that he found such a knife clipped inside Gray's pants pocket - was actually a legal knife, and provided no justification for Gray's arrest. Gray started running after officers made eye contact with him.

Mosby said Gray was assaulted by Miller, Officer William G. Porter, Officer Edward M. Nero, Lt. Brian W. Rice and Sgt. Alicia D. White. Each faces up to 10 years if convicted of second-degree assault.

The van driver, Officer Caesar R. Goodson Jr., faces up to 30 years on the murder charge, and 10 years each for involuntary manslaughter, assault and "manslaughter by vehicle." All of the officers also face a charge of misconduct in office.

At least five were in custody, Mayor Stephanie Rawlings-Blake said at an early afternoon news conference.

She promised to change the police department's culture.

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

Mosby said she comes from five generations of police officers, that she respects and honors how police serve the people, and that this case should in no way damage the relationship between police and prosecutors in Baltimore.

She swiftly rejected a request from the Baltimore police officers union asking her to appoint a special independent prosecutor because of her ties to attorney Billy Murphy, who is representing Gray's family. Murphy was among Mosby's biggest campaign contributors last year, donating the maximum individual amount allowed, $4,000, in June. Murphy also served on Mosby's transition team after the election.

Before Gov. Larry Hogan visited a fire station Friday, a man leaning out of a passing truck window pumped both arms in the air and yelled, "Justice! Justice! Justice!" When Hogan arrived, he said he was focusing on keeping Baltimore safe.

"I want to continue to ask for calm and peace," said Hogan, who on Monday declared a state of emergency and called in 2,000 National Guardsmen.

At the corner of Pennsylvania and North avenues, where the worst of the rioting took place on Monday, drivers honked their horns. When buses stopped in front of the subway station, people spilled out cheering as the doors opened.

There was no large gathering at the intersection immediately after the announcement, though: Nearly 100 police in riot gear were deployed, and for the moment, they had nothing to do.

Ciara Ford, of Baltimore, expressed surprise at the decision to prosecute.

"I'm ecstatic," she said. "I hope this can restore some peace."

"It makes you cry," said her friend, Stephanie Owens of Columbia.

They both hoped the officers would be convicted. And both believed that the protests in the city made a difference in ensuring that authorities took the case seriously.

"If we had kept quiet, I don't think they would have prosecuted," Ford said.

Community activist Ted Sutton surveyed the joyous scene with amazement. "You don't see people chanting. What you see is people celebrating," Sutton said.

The charges, and Mosby's detailed explanation of what happened, are a first step toward transparency, he said.

"She took the time to critique the evidence," Sutton said, noting that the officers faced different charges specific to their actual alleged misconduct. "To have each person charged with what they actually did . to have it come out this quick - this is something else."

Councilwoman Helen Holton said the decision to bring charges was a "defining moment" and noted other injustices against blacks, from Emmett Till, a teenager killed after flirting with a white woman in Mississippi in 1955, to Rodney King, who was beaten by Los Angeles police in 1991 to Walter Scott, who was fatally shot running away from an officer in South Carolina earlier this year.

"My God, how many more black men must die before we say enough? Hopefully, Freddie Gray will be the last. If not, it is my fervent prayer that Baltimore city will lead the nation to say, 'We will take down those who violate the rights of citizens, any citizens,'" she said. "I'm psyched today! I'm like, 'Whoo!' My feet are not even touching the ground."

Associated Press writers Brian Witte, Matthew Barakat and David Dishneau contributed to this story.