Upon learning that King Courtney and his men are after him and his money, Mike decides to strike back, he gets in a car and he kills 10 Yardies around Shoreside Vale in 4 minutes to weaken the Yardies.
Use the Pump Shotgun to quickly kill the Yardies. They will usually be down in one hit.
The F1 is helpful in this mission as it is the fastest vehicle in the game and can get you around Shoreside much quicker.
Although there are shortcuts, they involve ramps. Try to keep track of where they are beforehand, and be careful to not fall into the ocean.
The reward for completing this mission is $40,000 and unlocks the mission Assault Joint.