Climb Ev'ry Mountain

 is a quest in Fallout: New Vegas.

A sniper is killing NCR soldiers and civilian refugees in the Bitter Springs Refugee Camp. Captain Gilles wants you to track down this unknown assailant, who has been hiding in one of the hillside caves to the north of Bitter Springs.

Quick walkthrough
The sniper is located in a cave north-west of Bitter Springs (north-east of Bloodborne Cave), at the end of a small path. This path can be very difficult to locate as it is well hidden among rocks that cannot be climbed and are very easy to become stuck in. Just before the path you might find several fire geckos inhabiting some red rock; the path is just to the north, when you enter back into grey rock, and is slightly to the right.

Inside is Oscar Velasco, a member of the Great Khans who lost his family three years before and now seeks vengeance by killing the occupants of Bitter Springs. He can be convinced to let go of his anger and move on to Red Rock Canyon with a Speech check of 50; if successful he will also give the Courier a key that unlocks the gates to the supply caches located inside each of the caves for the quest No, Not Much.

Bugs
In the cave Oscar is hiding in, there is a gate to the left of the entrance corridor, and another corridor to the right, opposite the gate. If you follow this corridor, there is a bear trap on the floor near the beginning, and three frag mines near the end. The mines are lined up across the corridor with the one on the right sitting still and unarmed, while the two on the left are glitching in and out of the corridor floor. These two frag mines are also unarmed, but much more difficult to pick up.

Even if you've been to the cave on top of the mountain and completed the Quest, you'll get the reward, but, the quest will still be in your Pip-Boy as if you haven't completed it.