'Everest' cast endured sub-zero temps, altitude training and ATTACKING YAKS?!

Everest, director Baltasar Kormákur's drama based on the true story of climbers getting caught in a severe storm on Mt. Everest (the same source material as the book Into Thin Air), aims for authenticity. The film's A-list stars, including Jason Clarke, Jake Gyllenhaal, John Hawkes and Josh Brolin, trained to climb like their characters did, and did plenty of filming actually on Everest. The actors endured altitude training (Gyllenhaal and Brolin purposefully did a little too much training and got weird), filmed in -22°F (-30°C) weather and spent plenty of time in close quarters with their cold co-stars.

Kormákur was prepared to face those challenges once he determined he would film in an avalanche-prone area. But here's one thing he didn't plan for: aggressive yaks.

Kormákur told Paste BN at the Everest premiere what happened while he was shooting a scene with the animals on the mountain.
"We had a helicopter coming to shoot it wide, but the yaks were not used to the helicopter," He said. "The yaks come running."
Suddenly, the frightened animals went charging for actress Naoko Mori, who plays a climber standing on a bridge 1,000 feet in the air.

But don't worry, his actors saved the day.
"Josh Brolin stopped the yak. Josh and Jason (Clarke), they did it."

Heroes!