BALTIMORE, Maryland -- Latest developments:
• President Barack Obama has spoken out about the decision to charge six police officers in the death of Freddie Gray, saying it's vital that the truth comes out. He also expressed his hope protests will continue to be peaceful.
• In an open letter to Baltimore State's Attorney Marilyn Mosby, the city police union's president said none of the officers was responsible for Gray's death. "To the contrary, at all times, each of the officers diligently balanced their obligations to protect Mr. Gray and discharge their duties to protect the public," wrote Baltimore City Fraternal Order of Police President Gene Ryan.
• Ryan asked in the letter, which came out just before Mosby announced that six officers face charges in Gray's death, that a special independent prosecutor be appointed to look into the case.
Baltimore's prosecutor brought charges Friday against six police officers in the death of Freddie Gray, saying he suffered "a severe and critical neck injury" as a result of being placed "handcuffed, shackled by his feet and unrestrained" inside a police van.
The most serious charge: second-degree depraved-heart murder for the driver of the van, Officer Caesar R. Goodson Jr.
"To the people of Baltimore and demonstrators across America, I heard your call for 'No Justice, No peace,' " Baltimore City State's Attorney Marilyn Mosby said. "Your peace is sincerely needed as I work to deliver justice on behalf of this young man."
In addition to the charges against Goodson, another officer was charged Friday with several counts, including manslaughter and involuntary manslaughter. Two other officers face charges including including involuntary manslaughter. An additional two officers are charged with several counts, including second-degree assault.
Warrants have been issued for the officers' arrests. The officers are expected to be arraigned Friday, according to a source with knowledge of the proceedings.
Mosby's announcement brought cheers from onlookers at her news conference. Motorists in Baltimore honked horns and support exploded online.
"Let me tell you I just sat and watched Marilyn Mosby speak and as she announced everything I shed a tear..someone finally got it right," Twitter user TaviBabi wrote.
Prior to the announcement, protesters had planned at least four rallies in Baltimore to express their frustration with what they said was a slow pace of the investigation.
Other demonstrations were scheduled in Chicago, New York, Seattle, Dallas, San Francisco and Oakland, California.
The mother of Trayvon Martin, the African-American youth killed in 2012 by neighborhood watch volunteer George Zimmerman, plans to attend one of the Baltimore rallies, the Rev. Jamal Bryant of Baltimore's Empowerment Temple said in a tweet.
Authorities pleaded for patience Thursday after police said they'd finished their investigation, but wouldn't publicly release their findings. Police turned their files over to prosecutors.
"We ask for the public to remain patient and peaceful and to trust the process of the justice system," Baltimore State's Attorney Marilyn Mosby said Thursday.
For the most part, that patience held Thursday night. Marches were peaceful in Baltimore, although police in Philadelphia clashed with protesters as officers tried to prevent them from blocking a highway.
Police statement raises more questions
While the police investigation is complete, Mosby's office said her office will conduct its own inquiry.
"We are not relying solely on their findings, but rather the facts that we have gathered and verified," she said.
On Friday, the state Office of the Chief Medical Examiner handed over the autopsy report to Mosby's office, a source in the office told CNN. The report's findings have not been made public.
In the meantime, the mystery of how the 25-year-old died has only grown more complex.
Police revealed Thursday a transport van carrying Gray made an additional stop after his arrest April 12. Deputy Police Commissioner Kevin Davis said the stop was recorded by a privately owned video camera, arousing suspicion among protesters who wondered why it was not previously mentioned.
The video belonged to shop owner Hwang Jung, who said police copied the footage. The original was lost when his store was subsequently looted, he said.
The new stop, Davis said, came between the first and second stops. Before it surfaced, police had spoken of three stops before arriving at the police precinct -- one to put leg irons on Gray, a second "to deal with Mr. Gray," and a third to pick up an additional prisoner.
That second stop remains under investigation.
Mosby did expand on how Gray may have died. "The manner of death deemed a homicide by the Maryland state medical examiner is believed to be the result of a fatal injury that occurred while Mr. Gray was unrestrained by a seat belt in the custody of the Baltimore Police Department wagon," she said.
Police have said previously that Gray had not been properly fastened into the van, a violation of department policy.
Was it in the van?
An earlier report by CNN affiliate WJLA-TV in Washington, said Gray's injuries could have happened in the van. The police investigation did not find he died from injuries caused during his arrest, the station reported, citing "multiple law enforcement sources briefed on the police findings."
Instead, the station reported investigators believe Gray slammed into part of the police van, apparently breaking his neck. A head injury matches up to a bolt in the van, the station reported without mentioning how the injury may have happened.
CNN's Josh Gaynor, Pat St. Claire, Carolyn Sung, Evan Perez, Dana Ford, Don Lemon and Anderson Cooper contributed to this report.