A Chinese photographer accidentally captured the moment a massive ice-rock avalanche struck Mount Langtang Lirung in Nepal during a drone shoot on August 26. This has offered researchers new clues about the disaster that triggered a deadly chain of floods and landslides in the Himalayas.

On the morning of August 26, high in Langtang National Park near Nepal’s border with China, a massive wall of ice and rock suddenly broke loose.

The video, filmed by a Chinese tour guide in Tibet, shows huge chunks of ice breaking away from a ridge on Langtang Lirung peak, on the Nepali side of the border.