The transport van that carried Gray made a previously unknown stop along its route from where he was arrested to the police station. It was one of four stops police now are saying the van made.
What they haven't said yet, and what remains under investigation
, is how Gray suffered a fatal spinal cord injury. He died while in police custody exactly one week after his April 12 arrest.
Many believe the key to understanding what happened to Gray is understanding what happened inside the van.
When he was placed inside it, he could talk, according to videos and to Baltimore Deputy Police Commissioner Jerry Rodriguez.
"And when Mr. Gray was taken out of that van, he could not talk, and he could not breathe," Rodriguez said.
Here's a closer look at what we do and do not know about that controversial ride:
What we know: A police officer makes eye contact with Gray and another individual in a high-crime area of Baltimore. Gray and another person bolt, and the officer, along with others, gives chase.
Gray is stopped and "gave up without the use of force," according to Rodriguez.
Police call for a transport van, and officers drag him to it. Video shows Gray screaming in apparent pain. He asks for an inhaler, which he did not get.
What we don't know: Video from the arrest does not show the entire incident. It starts with Gray already on the ground. We don't know what happened before the cameras started rolling.
What we know: The van makes its first stop at 8:46 a.m. An officer asks the driver to stop so they can finish paperwork and put Gray in leg shackles. He is described by the driver of the van as "irate," according to Rodriguez. Gray was still able to move and talk at this point. We also know that Gray was not seat-belted in the van, as per police policy.
What we don't know: Was he actually irate? Was Gray injured during the stop? Several witnesses saw what happened, and have spoken to investigators. We don't know yet what they said.
What we know: This previously undisclosed stop was discovered from a privately owned camera, Deputy Commissioner Kevin Davis told reporters, without elaborating.
What we don't know: Authorities haven't said anything yet about why this stop took place, nor what happened. Each stop is supposed to be logged, and that didn't happen in this case.
"Obviously, it raises all kinds of questions. Somebody in the police department knew about this stop, and what it suggests is that whoever was driving the van, whoever was involved in the van trip was not forthcoming," said Bill Yeomans, a former Justice Department official.
What we know: The van stops for a third time "to deal" with Gray, Davis said last week, adding that the "facts of that interaction are under investigation."
Police Commissioner Anthony Batts, also last week, told reporters that officers picked Gray "up off the floor and place(d) him on the seat." Gray asked for a medic, Batts said.
What we don't know: As with the second stop, very little is know about this one.
What triggered the third stop? Why did officers suddenly have "to deal" with Gray? Why was he on the floor? Why did he ask for a medic? Was Gray's condition worsening? And if it was, as his request might suggest, why wasn't he provided medical attention?
What we know: The van's next stop involves a call for assistance from an unrelated arrest. The driver of the van decides to respond to that location, where a second prisoner is put inside the van with Gray.
According to Batts, that prisoner could not see Gray, but he could hear him, and what he heard was "Freddie thrashing about."
The same prisoner also told investigators he thought Gray "was intentionally trying to injure himself," The Washington Post reported.
What we don't know: There is no video from inside the van, so we don't know exactly what happened inside it. Was Gray intentionally trying to hurt himself? Or was he already in the throws a medical emergency? If he was trying to hurt himself, why did officers not do anything to stop him?
What we know: Both prisoners are taken to the Western District police station. A medic is called for Gray. He is later transported to the University of Maryland Medical Center, where Gray dies one week later on April 19.
A police investigation into his death found no evidence he died as the result of injuries caused during his arrest, according to CNN affiliate WJLA, citing "multiple law enforcement sources briefed on the police findings."
The sources quoted by WJLA said the medical examiner had determined Gray's death was caused by catastrophic injury after he slammed into the back of the police transport van, "apparently breaking his neck; a head injury he sustained matches a bolt in the back of the van."
What we don't know: Bottom line: We still don't know when and how Gray suffered his fatal injury, and when. The medical examiner's office has not released its report, which could take 30 to 45 days.