Mountain Base - Enemies with Fuel Barrel

Lara overhears 2 men talking in the hallway ahead as they haul some heavy object. Move to the door on the opposite side of the room. Ignore the salvage crate next to the door for now and peer out to the left.

If you're quick, you can catch the two guys moving a big, red barrel. Unless you're a fan of Watney's beer, the first thing that will come to mind will be explosions.

Use your bow to target the barrel and, once both men are standing close to it, let fly.

The resulting fireball should take out both of them. If not, finish off any survivors.

A third man comes down the stairs at the end of the hall to investigate. Take care of him as well.