Complex sentence: The police arrive and arrest Tyrell's remaining henchmen while Kellaway arrests Stanley again, Then Tilton announces to everyone that Tyrell was The Mask the whole time, as a way for Kellaway to let Stanley go.
Split into simpler sentences: The police arrive and arrest Tyrell's remaining henchmen while Kellaway arrests Stanley again, but is interrupted by Tilton. Telling Kellaway that Tyrell was The Mask the whole time, as a way for Kellaway to let Stanley go.