(AP) 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 lawyer, 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.

Police Commissioner Anthony Batts said that Gray asked first for an inhaler, and then several times during his transport for medical care.

"There were several times he made a medical request," Batts said. "He asked for an inhaler, and at one or two of the stops it was noticed that he was having trouble breathing and we probably should have asked for paramedics."

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 when he was taken out of that van, he could not talk and he could not breathe," Rodriguez said.

Batts also said it is still unclear why Gray was stopped in the first place, saying only that officers "made eye contact" with Gray and another man, and the two took off running.

"That's part of the question we have to dig into," Batts said, "if there's more than just running. There is no law against running."

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.