Sitting near chunks of concrete, bricks and a ripped orange sofa, Luo Shiqiang told how his grandfather was just returning from feeding chickens when their house collapsed and crushed him to death in a powerful earthquake in southwestern China.

“We lost everything in such a short time,” the 20-year-old college student said. His cousin was injured in the collapse, but other family members were spared because they were working in the fields in hard-hit Longmen village in Lushan county.

Saturday’s earthquake in Sichuan province killed at least 186 people, injured more than 11,000 and left nearly two dozen missing, mostly in the rural communities around Ya’an city, along the same seismic fault where a devastating quake to the north killed more than 90,000 people in Sichuan and neighboring areas five years ago in one of China’s worst natural disasters.

The Lushan and Baoxing counties hardest-hit on Saturday had escaped the…