BALTIMORE — Baltimore’s top police officials, mayor and prosecutor sought to calm a “community on edge” Monday while investigating how a man suffered a fatal spine injury while under arrest. Six officers have been suspended, but investigators say they still don’t know how it happened.

A week after Freddie Gray was pulled off the street and into a police van, authorities don’t have any videos or other evidence explaining what happened to cause the “medical emergency” an arresting officer said Gray suffered while being taken to the local police station, Deputy Commissioner Jerry Rodriguez said.

The Gray family’s attorney, Billy Murphy, had said that Gray’s “spine was 80 percent severed at his neck.”

Autopsy results returned Monday show that Gray “did suffer a significant spinal injury that led to his death,” Rodriguez said. “What we don’t know is how he suffered that injury.”

Police also released a more detailed timeline of how Gray was arrested and transported on April 12. It revealed that Gray was placed in leg irons after an officer felt he was becoming “irate,” and that the van stopped on its way to the police station, even picking up another prisoner in an unrelated case, while Gray repeatedly asked for medical attention.

Something must have happened between the time Gray was videotaped by a bystander being dragged into the van, and the time he arrived at the station in deep distress, the deputy commissioner said.

“When Mr. Gray was put in that van, he could talk, he was upset. And he was taken out of that van, he could not talk and he could not breathe,” Rodriguez said.

Mayor Stephanie Rawlings-Blake said she too is “angry that we are here again” after trying to overcome decades of distrust between police and citizens in Baltimore’s inner city.

Police Commissioner Police Commissioner Anthony Batts said he is ordering that police review and rewrite “effective immediately” its policies on moving prisoners and providing them with medical attention.

“We are a community on edge right now. We hear, I hear, the outrage. I hear the concern and I hear the fear,” Batts said, asking for calm. “We are on edge as a city, and I need your help to make sure we get this out in the proper way.”

All six officers involved have been suspended, said Rodriguez, who is in charge of the department’s professional standards and accountability.

Officer Garrett Miller’s official request for a criminal charge against Gray, a 25-year-old black man who was only 5-foot-8 inches tall and 145 pounds, said that he had been arrested “without force or incident.”

Miller sought a charge of carrying a switchblade, punishable by a year in prison and a $500 fine, according to court records. His charging document doesn’t provide any explanation for the injuries that would lead to Gray’s death a week later. He wrote only that while being taken to the station, on April 12, “the defendant suffered a medical emergency and was immediately transported to Shock Trauma via medic.”

Another 30 minutes passed before police finally called an ambulance to pick up Gray at the station. He arrived at the hospital in critical condition and died Sunday after a weeklong coma.

The documents, which misspell Gray’s name as “Grey,” were first reported Monday by The Baltimore Sun. Police had not previously mentioned a knife, nor publicly disclosed the charge against Gray.

“We have no confidence that the city or the police department is going to fairly and objectively investigate this case,” Murphy said.