Freddie Gray's fatal journey in the back of a Baltimore police van on April 12 still remains shrouded in mystery. But a new video may shed light on a key moment in the 45-minute journey that would ultimately lead to his death and spark massive protests over police brutality.

The video shows Gray sprawled halfway out of the van on his stomach with his legs hanging out the backdoor while he is surrounded by four Baltimore Police officers. A fifth officer arrives on scene and the men stand over Gray. They appear to place shackles around his ankles.

Gray's death ignited outrage in Baltimore and days of large scale protests over police brutality gripped the city followed his April 27 funeral.

The cell phone video, taken by a bystander who witnessed Gray's April 12 arrest, was posted by the Baltimore Sun on Wednesday. An anonymous neighbor recorded the video on the corner of Baker and Mount Streets, just one block away from where Gray's initial arrest took place.

When police officers first shoved Gray into the back of a van on the morning of April 12, one of his legs appeared limp and he was able to speak. He was placed in handcuff with his legs unrestrained. On an earlier video of the arrest, he can be heard screaming in pain.

The new footage shows the first time that van stopped and Gray was removed, placed in leg shackles, and then again shoved into the back of the police van, this time on his stomach, entirely unrestrained.

It was after this stop that Baltimore City State's Attorney Marilyn Mosby says Gray likely suffered the severe neck injuries that led to his death. Her office's investigation into his death, which led to criminal charges against six Baltimore Police Officers, determined that Gray's homicide was a result of injuries he sustained while he was shackled but unbuckled in the back of the police van.

Mosby's detailed and damning account of the violent arrest focused in on this exact moment and the four police officers involved: Lt. Brian W. Rice, Officer Garrett Miller, Officer Edward Nero. The officer who drove the van, Caesar Goodson Jr., also appears to be present in the footage.

In the first of four stops that the van would make, Rice, Nero and Miller took Gray out of the van and put him in flex cuffs and leg shackles, said Mosby.

The officers also completed paperwork while there. In one of her most damning revelations, Mosby said that after Gray had been fully restrained, he was placed back in the van head first on his stomach, and that this led to serious injury.

"Officer Miller, Officer Nero, and Lt. Rice then loaded Mr. Gray back into the wagon, placing him on his stomach head-first onto the floor," said Mosby. He was sent to Central Booking and, en route, "suffered a severe and critical neck injury as a result of being handcuffed, shackled by his feet and restrained inside the BPD wagon."

The driver of the police van, Goodson, has been charged with the most serious offenses in Gray's death, which include a second degree depraved heart murder charge.

The officers charged with Freddie Gray's death. Top row from left, Caesar R. Goodson Jr., Garrett E. Miller and Edward M. Nero, and bottom row from left, William G. Porter, Brian W. Rice and Alicia D. White. Image: Baltimore Police Department via AP/Associated Press

Multiple officers repeatedly ignored Gray's medical condition during the journey. After Gray's initial arrest (stop 1 on the map below), the police van carrying Gray stopped four times before he was eventually taken to the hospital from the the Western District Police Station (stop 6 on the map below.)

It is unclear if police investigators or the State's Attorney have seen this new footage. Michelle Gross, whose neighbor used her phone to record the scene and then shared it with the Baltimore Sun, told the newspaper she has not been contacted by police.

Gross told the Baltimore Sun she could not understand why the police van made the stop that she witnessed.

"He was just laying there. If he already had cuffed him, what did they take them off for, what was the reason from point A to B," said Gross. "Why was he out? What happened in the back, we don't know but something happened."

The office of Baltimore City State's Attorney did not immediately respond to requests for comment on the investigation.