In the early hours of Saturday morning, rangers at the Khao Yai National Park in Thailand heard loud elephant calls coming from a ravine.

They arrived at a grim scene: six dead elephants, seemingly killed by a raging waterfall known as Haew Narok—or “Hell’s Abyss.”

No one witnessed the incident, but track patterns at the site, along with elephants’ known tendency to form close social bonds, lead park officials to believe that a calf fell over the waterfall and five adults died while trying to save it.