Ok theoretically, if they where going to let him go in the future, he would just be able to come back and warn himself that he was going to get caught and none of this would ever happen. Therefore, they must keep him in custody and possibly kill him inorder to keep the <¿>temporal linearity. If not, our whole fabric of time will be ripped apart and our universe will be deystroyed, c'mon people you've seen the friggin movies! Time travel is impossible anyways. Oor he is just a huge liar working with some evil ass people that know insider secrets that got him a fake identity and will probably torture him and possibly his family very badly if he rats them out so he made up some stupid ass story.