This is in the last mission of the game. After the two cars drive into the garage, go down the hill and stand at the top of the ramp. You might have to walk down a little to trigger the car. A car will come speeding up the ramp in front of you and you have to shoot the driver. The car goes to the right of the ramp so I suggest standing on the left side. Shoot as many shoots as you can at the front windshield and you should kill him. If you don’t get it on your first try then just reload the last checkpoint.