This Camp has 13 occupants that you need to kill. There’s a sniper overlooking the entire camp on the northwest side so I suggest circling around the camp and taking him out first.
Once he’s gone, you can circle around and enter from the rear gate of the Camp. There’s a few patrols here but they can be isolated so you can pick them off one by one.
Continue working your way on taking out the patrols, leaving the ones having a friendly brawl in the middle. When you’re ready, sneak close so you can throw a molotov or explosive to kill some of them at once. Finish off the remaining enemies so you can search for the Bunker.
Once clear, you can find the Bunker’s hatch behind the rocks to the northeast side of the Camp, past the two white cars near the fence. Examine the Map inside to clear the Ambush Camp.