The first thing you'll probably want to do, is to restock on weapons. By now you should have access to the Desert Eagle, SMG, M4, Sniper Rifle, and the heat-seeking RPG. For this mission, you will at least need a weapon capable of being used in a drive-by.
Head off to the base of Mount Chiliad, and then to the snitch's house. Ascending the mountain can be somewhat awkward in most vehicles, so an off-road vehicle such as a Sanchez bike is recommended. You can find one at the end of the Chiliad Challenge route.
As you approach the house, a brief cut-scene explains the situation. Take out the guards from a distance if possible, then approach the house. When you get nearby, the snitch will take off in a Washington car. Jump on the nearby Sanchez, and follow him. Use drive-by to damage the car, but be careful not to destroy it. If the snitch's corpse is unidentifiable, you fail the mission.
When his vehicle is sufficiently damaged, he will jump out of the vehicle. Finish him off, then take a photo of the corpse. Now just return to the trailer park to complete the mission.
- If you approach the house before killing all the guards, the snitch may not make a run for it, and you can kill him easily without having to chase a car 'round a mountain. This can be easily done by staying deep in the woods to the left.
- The best way to kill the snitch without him running is to bring a sniper rifle and approach the house from the west from a distance. If you aim your sniper rifle you should see a part of his body and one shot can kill him.
- Another way is to stealth into the house. It's possible to shoot him point blank from behind him without him ever moving.