when your on the bike he is in a boat, you have to follow him by going along the beach.
SPOILER !!!!!!!!!!!!!!!!!!!!
Eventually you have to hit a ramp and your hanging onto a helicopter in the cutt scene. You have to tap A inorder to climb into the helicopter. You then take control and have to dodge rockets fired from the boat only one is unmissable. After the cutt scene run after jimmy and friends and kill them triggering the last cutt scene.
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