Park Chol-hee was working a holiday shift at Samsung Heavy Industries' Geoje shipyard on Labor Day in 2017 when a giant crane collided with another and crashed to ground, killing six people, including Park's younger brother.

"It was as if a bomb was dropped," Park said. "Bodies were too damaged to describe."

Park and his brother, Sung-woo, were among nearly 1,500 subcontracted employees — 90 percent of the shipyard workforce that day — building an oil and gas platform for the French energy giant Total.