Suman Semwal described how his father, who lives in Mukhba village of Uttarakhand's Uttarkashi, heard a rumbling noise from Kheer Ganga, followed by an unimaginable rush of water and debris. He, with others recording the incident, tried to alert the people downhill through whistling. "People couldn't comprehend what was happening. The flood waters struck them in 15 seconds," Semwal said.