how do you kill it since as soon as the cut scene ends it kills me?

To destroy this boss, you must move to the right of the door straight away, preventing you from being attacked by the things tenticals. Shoot the wooden boxes on the left side of the room, then shoot the thing like mad until a tentical comes out of the vent to the right, you must move across to the left, close to the boxes you destroyed but making sure your in a position where the thing cant hurt you still. The thing should ventually smash down the blockade that is right next to you. Then you are to shoot the tentical to the right and when its health is low throw a flame grenade at it to kill it for good.
You must then shoot the thing until a body part resembling a scientist pops out of it at the top, you can then burn it to death, and it will die in due time.

To exit the level fix the door circuit and your done. Remembr that the aliens are not resistant to fire.

Man I have trouble beating him with 5 medikits, this guys is tough only played him once though.

don't fight the boss just fix the junction box you should only use 1 medkit and lose half of your life

quote Barney Calhoun

don't fight the boss just fix the junction box you should only use 1 medkit and lose half of your life