Take a look at the following video.
I watched this with some senior warrant officers yesterday, and we all instantly recognized the culprit: the rapid transition from an in-ground-effect (IGE) condition to out-of-ground-effect (OGE). (A brief aerodynamics lesson).
Certainly, it's impressive that the pilot cold pick up a firefighter while balancing the aircraft on the tips of its skids on the side of a mountain. Yet all the fancy stick-work in the world simply can't compensate for the inevitable laws of physics. This aircraft was too heavy for OGE conditions (just look at the coning of the blades). Despite the pilot's attempt to gain airspeed, he simply did not have sufficient power for the maneuver. The sad thing is, this sort of accident is preventable.
Let's take a look at what TC 1-237, the UH-60 aircrew training manual, has to say on the topic of VMC takeoffs, specifically, from pinnacles:
MOUNTAIN/PINNACLE/RIDGELINE CONSIDERATIONS: Analyze winds, obstacles, and density altitude. Perform a hover power check. Determine the best takeoff direction and path for conditions. After clearing any obstacle(s), accelerate the aircraft to the desired airspeed.
Performance planning isn't sexy, yet no one can doubt its importance. Flight school students learn performance planning before they even set foot in the cockpit. I can't help but ask whether or not the pilot filled out a performance planning card, did a hover power check, and confirmed OGE power for the mission. Those simple steps could have easily prevented this entire situation from taking place.
Fortunately, no one was seriously injured in this accident.
Link: US Department of the Interior accident prevention bulletin on rotary-wing performance planning.