On the sinking ship, when he attacks you from a helicopter?.. I've tried many things. First of all, no amount of rockets seem to be able to take the helicopter down. I've also tried sniping him, and hit him no less than 4 times with the sniper rifle, and he still refuses to die. Running away is also, not an option; Even if I reach the shore, he will catch up quickly, and on the shore, there's a whole lot of nothing... nowhere to hide, no turrets to use. Hiding ON the ship also doesn't work-- it's sinking.