At the beginning of the game, ONLY shoot the first 3 STAAR team members you see. If you did this right you will enter Kronn Hunter Mode.
In this mode you are a mercenary from the Kronn hierarchy sent to sterilize Area 51 of the Kronn rebels. You will notice that the grenades, bullets, shotgun shells, and machine gun bullets have taken on a Kronn form. You will also gain 20,000 points whenever your score is tallied, and you can shoot STAAR team members with impunity!
At the 7 level, shoot all the yellow barrel explosives. You will get to go to a secret room, called Chow Palace.