Newly released police video of a March incident that led to a Black man's death in Rochester, New York, shows officers covering his head with a "spit sock" and holding him on the ground before he stopped breathing.

Daniel Prude was having a mental health episode on March 23 when his brother Joe called the Rochester Police Department for help, the family said at a press conference Wednesday.

Prude stopped breathing after police knelt on him while he was naked and handcuffed, according to video. When he was brought to the hospital 15 minutes later, he was brain dead, his brother said.

Prude's death was ruled a homicide by the Monroe County Medical examiner, according to a copy of the autopsy report obtained by lawyers for his family.

The report cites complications of asphyxia in the setting of physical restraint as a finding. The report also cites excited delirium and acute PCP intoxication as causes of death.

Speaking at a press conference Wednesday, Joe Prude said police had killed a defenseless Black man and called his brother's death "cold-blooded murder."

Elliot Shields, one of the Prude family lawyers, said attorneys are in the preliminary stages of filing a wrongful death suit. Shields said that one of the reasons the family hadn't spoken publicly about the incident before was that it took time to obtain the body camera footage and there were no other recordings of what happened.

Daniel Prude's family speaks at a press conference on Wednesday.

Family members connected the killing to the broader movement pushing back against police violence toward Black people.

"How many more brothers got to die for society to understand that this needs to stop," Joe Prude said. "And I can't even share with y'all the pain that I'm feeling, and my family is going through as well."

Organizers from the group Free the People Roc, a Black Lives Matter group, named three officers they say were involved in the incident. CNN is working to confirm their identities and is not naming them at this time. 

Family members are calling on the firing and arrest of all the officers involved in Prude's death.

The bodycam footage

Disturbing bodycam footage of the incident, which was provided to CNN by attorneys for Prude, compiles multiple officers' body cameras and has been edited together to show different angles of the incident.

The video begins at 3:16 a.m. with Prude naked on a wet street as a light snow falls.

An officer exits his patrol car, approaches Prude while asking him six times to get on the ground as the officer points a Taser at him. Prude complies and is asked to put his hands behind his back, which he quickly does. The officer then cuffs him as Prude says "yes, sir" several times.

Several other officers arrive on scene and one appears to identify Prude by name.

While handcuffed, Prude repeats the phrase "in Jesus Christ I pray, amen." He also makes various remarks about getting his money to take a plane, and he asks for the officers' guns and that they stay away from him.

Three minutes after the incident begins, one officer puts a spit sock -- which is designed to keep a person from spitting or biting -- over Prude's head. He rolls around on the ground yelling various things.

Prude appears to try to stand at approximately 3:20 a.m., and three officers move in to restrain him and hold him to the ground. Police say Prude is spitting and appears to have vomited. Three minutes and 10 seconds after the restraint, an officer says "he started throwing up, now it looks like he doesn't even have chest compressions." 

They call in the EMT to help who instructs an officer to roll Prude over and perform chest compressions, which they do.

Prude appears non-responsive and is loaded into an ambulance at 3:27 a.m., 11 minutes after the first officer arrived on scene.

In the autopsy report, medical officials cite acute myocarditis and a history of severe respiratory acidosis. They stated Prude also has a clinical history of agitation and combative behavior, as well as a clinical history of suicidal ideation and possible auditory hallucinations and paranoia.

NY Attorney General's office investigating

Attorneys for the family say the video shows that officers mocked and teased Daniel, left him on the ground while handcuffed and naked and put a bag over his head. 

An investigation is currently in the hands of the New York Attorney General's office, Rochester Mayor Lovely A. Warren and Chief of Police La'Ron D. Singletary said when they addressed reporters later Wednesday and offered condolences to the Prude family.

Singletary told reporters that none of the officers involved in the incident are suspended, pending the outcome of the attorney general's investigation. The attorney general officially took over the case on April 16, Warren said. 

Singletary also said that the morning after Prude's encounter with police, he opened both a criminal and internal investigation into the incident. Warren said that after Prude died, she was informed by the Rochester legal department that this investigation was within the purview of the attorney general and nothing could be done on a city level until that investigation finished.

New York Gov. Andrew Cuomo signed a bill into law in June that designates the attorney general as an independent prosecutor for matters relating to the deaths of unarmed civilians caused by law enforcement. The measure is technically codifying an executive order Cuomo mandated in 2014 in the wake of Eric Garner's death after he was placed in a chokehold by a police officer.

"The death of Daniel Prude was a tragedy, and I extend my deepest condolences to his family. I share the community's concerns about ensuring a fair and independent investigation into his death and support their right to protest," New York Attorney General Letitia James said in a statement released Wednesday, in which she acknowledged an active investigation.

While neither the chief nor the mayor would provide specifics of the incident or discuss what can be seen on police body camera footage, Warren acknowledged that as soon as the attorney general's investigation is over, authorities will be able to give the family the information they deserve. 

Warren also said the date of death was March 30, a week after the incident. 

The attorneys for the Prude family say there are "no questions when everyone sees body cam videos, they are going to see a murder."

By: Taylor Romine, Benjamin Norbitz and Madeline Holcombe 

cnn.com