the prisoner who rode in a police van with freddie gray on april 12 in baltimore says gray was trying to hurt himself .
prisoner 's statement to investigators was part of an affidavit obtained wednesday by the washington post .
gray was arrested on april 12 for carrying a switchblade and transported to the hospital shortly after arriving at jail .
he died a week later from spinal injuries ; how he received the fatal trauma is still under investigation .
the fellow prisoner 's statement is the first detail released about what happened during the ride .
report was released as family member of one of the six suspended police officers came forward to defend the cop .
the anonymous relatives says she believes gray was injured before he was put in the van , and that not all six officers are to blame .