When they arrive 343 Guilty Spark warns them that activating this Halo will destroy the whole Ark and the Halo itself. The player ignores the warning. This angers 343 Guilty Spark. He kills Sergent Johnson, and attempts to kill Master Chief to keep'his' Halo from being destroyed. This is in effect the final 'boss battle' of the game. The player defeats the robot, and activates the Halo. A countdown starts but it too late for the player as Master Chief and the AI Cortana. They manage to board a spacecraft to take them away but it is caught in the explosion and is split in two. Master Chief is assumed dead.