medical examiner ` found freddie gray 's catastrophic head injury was consistent with bolt in the back door of the police van '
police report suggests he was standing and fell head first into the door .
officer driving van has yet to give statement to police , sources claim .
report on freddie gray 's arrest and death handed to state 's attorney at 8.50 am et on thursday .
it includes admission that police van made a previously unknown stop .
police commissioner refused to elaborate on the information .