"He was not well at the time and I thought this would cheer him up.''
Like Mr Butler, his father - who has since died - and his brothers loved Westerns.
Almost three years later he found the story he had written for his father lying around and decided to hinge it around the events of 1885.
Then he could not stop writing. It got to the point that his wife, Lee, asked if he would be getting dressed some days.
"Are you gonna actually get out of your dressing gown or you still going to work on your book? [she'd say].''
By early 2017 he had finished the book and tweaked it, but then it took a while before he gave it to someone to read.
He was persuaded to submit it to a publisher and eventually it was published by Outlaws Publishing, which specialises in Western novels, in a kindle version about a month later.
The paperback edition has been available since late January and he has been signed up to a five-year deal and has already committed to writing a prequel and a sequel to Corday's Law.
Mr Butler has never been to the United States, never mind Rock Springs or Sweetwater County where his novel plays out.
"The landscape and scenery I got from films I had seen and books that I had read.''
The 60-year-old father of two daughters, who co-owns an office supplies business, said his first royalty cheque had arrived, but he was a bit hesitant to look up how many books he had sold.
"It's all a bit surreal.''
Whether the book will be made available in New Zealand is yet to be determined, but Mr Butler hoped there could be an agreement reached with the publishers to get some local sales going.
giordano.stolley@odt.co.nz
