This mission unlocks after you take over the outpost Death Camp.
After the conversation finishes, three marker will appear on the map. First, go to the east-most one. You will run into a tiger over a corpse there. Kill the animal, or scare it away, approach the corpse and take a photo with your camera.
Go now towards the south-most marker. To climb the hillock, take the hillside to the right which is not as steep (the screenshot).
Once you reach the peak, you will encounter three pirates that need to be killed. The corpse that you are looking for is in the western part of the bump.
The last corpse is leaning against rocks at the roadside. After you take the third photo, return to the village to talk to the questgiver.