Badlands - Grand Theft Auto: San Andreas
Right after the “The Green Sabre” mission in Sweet's mission line, you are brought to Flint County by officers Tenpenny and Pulaski. Before you can move on to San Fierro, you'll have to complete some missions in Flint County, Whetstone and Red County. You've been stripped of all weapons, but luckily there is a small Ammu-nation in Angel Pine.
Step into the red marker that the ‘CJ' symbol on the radar is pointing to when you're ready to get started. Drive into the red marker at the foot of Mt. Chiliad and start up the mountain trail. The witness' log cabin is partway up the trail, its surrounding area patrolled by FBI officers. Make your way up the mountain and take a left when you reach the fork (the right path is blocked).
When you spot the cabin, crouch down and move behind the trees around back. You'll have to sneak in through the cabin's back door, so wait until there are no officers walking along the back of the cabin, then head for the door and slip in. Kill the suspect, photograph the body and hightail it out of there. There's a motorbike by the front door; hop on for a quick escape. Return to Angel Pine and drop off the camera to complete the mission.