A San Francisco man watched Tuesday's deadly earthquake in Nepal — already reeling from a quake earlier this month that killed more than 8,000 people — reduce parts of an ancient Hindu temple into "clouds of dust," he told NBC News. "It seemed like it would never stop," David Chen said. "It felt like the building was swaying back and forth." Chen was on a rooftop about to shoot drone footage of the temple outside Kathmandu, in the hopes of helping to map sites damaged in last month's temblor, when the new quake hit. He still managed to film the new quake on his cellphone, in footage that showed "a lot of clouds of dust" and nearby homes collapsing.