The sun poked through small breaks in Nepal's overcast skies on the brisk spring morning of April 25, 2015. The day started like any other, but at 11:56 a.m. local time, it turned deadly.

A powerful 7.8-magnitude earthquake gripped the region, sending residents scattering as buildings swayed and crumbled with the ground's convulsions. Numerous landslides careened down the rugged terrain—and a deadly avalanche swept down Mount Everest.

The human toll was staggering. The events killed nearly 9,000 people and injured thousands more. The Gorkha earthquake, as it came to be called, left nearby towns and cities in ruins, destroying more than 600,000 houses. Nearly four years out, with billions of dollars already spent, recovery is ongoing.

But