Hatherley's son, Felyx Hatherley, died at Point Lumber in Washdyke after a log rolled on him in March 2016.
Charges were later laid against the Timaru lumber yard.
Chadae Preston, Felyx's mother, and Hatherley, told Stuff the lumber yard was Hatherley's former workplace.
They said they were "gutted" about the charges.
Preston told Stuff Felyx had been climbing on the logs when they fell on him.
She said she had taken Felyx to visit his dad at work when the accident happened.
"He climbed up, and I told him to get down before he fell, so he climbed back down again," she said.
"Then he turned around and climbed up one, and that just sent them all tumbling down."
A death notice for Paul said he was the "much loved son of Pete and Margaret, loved brother of Marc. Loved and cherished Dad of the late Felyx. A much loved uncle of all his nephews."