You might be right, I'm not ruling anything out. That still doesn't (imho) cover the "why now" question. Since there seems to have been a tight lid on this, why the sudden need to tell everyone?
Maybe to beat the civil libertarians who would make a fuss about it. The decision to make him eligible for the military tribunal was probably just made and the man has been transferred to a military base.
The administration has been burned pretty bad about not "telling" us things.