"I was actually writing a script set in the bush of Wanganui when someone told me it sounded similar to the story of Robert Hansen."
Walker was captivated by the story and scrapped his original idea.
His family, who live in New Zealand, are astounded by his success.
"I had some aunts come to the set and they were like 'oh, you are filming next to a trailer park' and I had to tell them those were the caravans for the actors and set workers."
Walker misses his home country, which he says is a grounding reprieve from the ego-filled movie industry.
"New Zealand has a terrific reputation, not only from a creative perspective but in terms of people."
The Frozen Ground is due to be released in New Zealand this November.