There are 6-7 people you have to shoot. First of all, make sure you're on the roof of the building closest to the ship. It makes it a lot easier, you'll be able to see all the guys on the ship.
There are 2 on the dock, shoot them first. Then shoot the guys at the top of the ramp leading up to the ship.
Move your aim to the right, you should see a few more guys around some boxes, i think there's 3. Take them out.
That's all you have to do, 8-ball will do the rest. Good Luck! :thumbsup: