One element that I want to bring into the experience of Siege is a sense of being out of control. The Police player must feel as though his character doesn't control the whole situation. If the Police did, there would be no danger to the Hostage. Likewise, the Hostage player must feel out of control because the Hostage is in peril. And the Hostage-taker (still working on a better name - suggestions are welcome) isn't in control, otherwise they'd have what they were demanding.
To facilitate this, many of the narrative declarations about characters will be contributed by the other players. In doing this, the player will experience the unfolding of secrets and facts, as well as the uncertainty of being out of control.