A prisoner who was riding in the same police van as Freddie Gray the day he was arrested said he believes Gray "was intentionally trying to injure himself," according to a police document obtained by The Washington Post.

On April 12, the unnamed prisoner said he was inside the vehicle during the ride to Baltimore's Western District police station. Though he did not see Gray because he was separated by a metal partition, the prisoner said he could hear him "banging against the walls."

After the 30 minute ride, Gray's unconscious body was taken from the van to a hospital where he died April 19 from a spinal cord injury, sparking turbulent protests all over Baltimore and in other states.

The prisoner's statement, given to Baltimore police, was part of an application for a search warrant, The Washington Post reported. The newspaper was given the statement by a person on condition of anonymity over concerns for the inmate's safety. The prisoner's name was not released.   

Details surrounding how Gray, 25, fatally injured his spine are still murky. Police said they do not know if he was injured during his arrest after officers chased him through West Baltimore. Video of the incident shows police pinning Gray before forcing him inside the transport vehicle.

It's also unclear if his spine was injured during the ride, which included three stops- the first to put leg cuffs on Grey, the second when the driver requested that Gray be checked on and the third when another prisoner was placed into the van.

There is no mention in the affidavit of how many officers were in the van or if they heard any banging, The Washington Post reported.

Gray, who was not wearing a seatbelt inside the van, asked for medical attention several times but was ignored, which Baltimore Police Commissioner Anthony Batts said was a mistake on the officers' part.  

Baltimore Police Department spokesman Eric Kowalczyk declined to comment on the affidavit as the department's investigation into Gray's death is ongoing. Once completed, the findings will be turned over to the state attorney's office in Baltimore, The Washington Post reported. In the meantime, six officers remain suspended.

Gray's family said they were unaware of the prisoner's statement.

"We disagree with any implication that Freddie Gray severed his own spinal cord," Jason Downs, the family's lawyer, told the newspaper.

"We question the accuracy of the police reports we've seen thus far, including the police report that says Mr. Gray was arrested without force or incident."