A flash flood, meaning a torrent that rises within hours rather than days, tore through the border region between Nepal and China's Tibet Autonomous Region last week, killing more than 600 people and leaving more than 3,000 unaccounted for. One of those missing is Jitendra Patel, an American who had been traveling to Mount Kailash on a spiritual pilgrimage. His son, Sunny Patel, recognized his father's location from viral footage of the disaster circulating online.

Sunny said he watched the video and, about 30 seconds after taking in the scale of the destruction, it registered. He texted his mother, hoping she had not yet seen it. She had. "That's exactly where he was," she told him.

Sunny last spoke to his father on Wednesday morning. He believed his father had already crossed the border from Nepal into China by then, but he has not been able to confirm that.

What set off the flood

The flood appears to have started when a large section of glacier broke away and fell into the Lhende Khola River, sending stories-high waves of rock, ice, and debris through the mountain river systems along the Nepal-China border. Newly released figures put the death toll at more than 600. More than 3,000 people remain missing. Over 4,000 have been rescued.

Jitendra was traveling with a group heading to Mount Kailash, a peak in Tibet that draws thousands of pilgrims for religious journeys each year. The group had planned to arrive a day earlier but was delayed by car trouble. That delay, Sunny said, may have put his father directly in the path of the disaster.

A wall of silence from the Chinese side

The most difficult part for the family, Sunny said, is the near-absence of information from the Chinese side of the border. They have spoken to embassies in Kathmandu and Beijing and have reached the U.S. State Department. Missing person reports have been filed with multiple agencies.

"We're trying to go on these media segments and get the awareness out there that there are people on the Chinese side that we aren't getting a ton of information about," Sunny said.

Search and rescue operations were suspended Saturday because of rain and heavy fog. Two lakes that formed upstream as a result of the disaster are being monitored by authorities, and one was overflowing at times as of the latest reports.

Sunny described his father as irrepressibly upbeat, a man who answered "How are you?" the same way every time: "I'm the best, God is great."