to beat the boss, first just kill all the normal people until you get to the boss. Whenever you can, use bezerk when he is shooting the large red balls. then hit him while he is shooting the flashing balls with strafing and use bullet time if you need to. Keep on doing this until he is dead.
i don't like this... my character can't move and you can't beat any of the creatures because they don't die, so what is the point? also, the things don't attack back so its basicly an endlesslly repeating animation.