He said the investigation was ongoing and didn't comment further.
Detective Senior Sergeant Richard Quested from Timaru confirmed both parents were at the business with the boy.
"He's just devastated," he said of the dad.
"His son was his whole world and now he's not there. He's absolutely distraught."
Police would also be interviewing the boy's parents and the owner of Point Lumber today.
"There will be other interviews out of that once we collate the information that we've gathered."
One other employee was also at the business, but in a different area, he said.
Mr Quested confirmed the father was on his way to hospital with his son where he came across a police officer.
The officer took Felyx in his car and rushed him to hospital, he said. The boy later died of his injuries.
Felyx's death was referred to the coroner.