In order to defeat him, throw everything you have at him. He has no weak point. Make sure you have a Magnum (level 4), assault shotgun (level 4), and MRL (level 4). Use the Magnum first. After you shoot him enough times, he will jump onto the rooftop and run around to a certain spot, where he will shoot his tentacles down the wall and pop up directly in front of you to attack. This cannot be dodged. He will then jump up and attempt to crush you. Dodge this, and repeat the process. When you run out of ammo for the Magnum and assault shotgun, use the MRL. Shoot all eight rockets at him. If he survives, finish him off with the handgun. Note: He can grab you and hold you in the air. This will damage you until you die or shoot him enough times to make him let you go.