As you are going up the stairs to chase Clarence, you will see a green health kit. Do not take it. Continue after Clarence and follow the advice of McCleary about not using your weapon until you are on the second floor; otherwise, Clarence will just get into a vehicle and leave. If you wait until you are on the second floor, he will climb to the roof. After you have chosen the Clarence's fate, you automatically have a three star wanted level regardless of what you selected. You must battle your way out. Because you are going down, you have a distinct disadvantage in cover and will take lots of damage. To give yourself an edge, at the start of the mission park a fast car on the street near the opening in the gate. Do not pull up to the gate. Use the stairs to your right to give chase. Once you have gotten to the roof and chosen his fate, descend to the level with the first aid kit (green box). Because you left it there on your way up, you will know what level you are on and can power up. Go to the side of the building where your car is parked and jump over the railing. Upon landing, you will not lose much health. Sprint to your car and get away from the cops. If done correctly, you should not take a single bullet from police. The health pack is a requirement to survive the fall.