From Lexicanum

Fire Warrior is an FPS (First person shooter) game for PC and PlayStation 2 based originally on the book of the same name. The game follows a Tau Fire Warrior, Shas'ui'T'au'Kais, and his heroic acts to save the Ethereal Ko'vash, while fighting against the forces of the Imperium (Notably the Imperial Guard and the Raptors).

Further into the game Kais, teams up alongside Captain Ardias of the Ultramarines 3rd company during a temporary cease fire negotiated between the two factions, this is because the forces of the Chaos Word Bearers intervene with the fighting on the planet. Eventually the planet is ordered to be cleansed through bombardment of an Orbital Strike ordered by Ardias to rid the planet of Chaos taint.

What happens to Shas'ui'Kais in the events afterwards is unknown.