Instructions
Arm yourself with as much weaponry as possible -- this includes rocket launchers, and multiple assault riffles and machine guns.
Park at City Hall in Staunton and kill the four Sicilians waiting outside. Jump out of your car and target them quickly with an assault riffle.
Drive east to the yellow beacon at the pier. Park your car, then step into the beacon on foot.
Shoot the gangster that appears below you, which will cause you to appear in the back of a speedboat. You'll now be at the helm of a gun turret.
Aim the gun turret towards the tail end of your boat and shoot the five pursuing boats, then the waves of enemies that follow.
Focus your fire on the helicopter as soon as it appears, then refocus your fire on the pursuers in the water. Your boat will then dock at the nearby lighthouse.
Exit the boat and begin working your way to the top. Target the two enemies on your left, then take out the mobster behind the boxes in front of you.
Shoot the last enemy at the top, then step into the beacon. This will cause the helicopter to appear.
Take out your Rocket Launcher and fire three times to knock the chopper out of the sky. This will officially complete the main story.