“I wish I wasn’t going out (to Moree) tonight,” he told his wife, Alison McKenzie, driving into Tamworth on July 29, 2014.

“I wish I was staying at home sleeping in our bed, with you by my side.”

His last words to her would become a wish that could never come true, as hours later, farmer Ian Turnbull, now 81, used a hunting rifle to murder the 51-year-old environmental officer.

Glen was on public land carrying out investigative work for the Office of Environment and Heritage (OEH) with a colleague, near the Turnbull's property at Croppa Creek, when he was confronted by Turnbull and shot in the neck in the early hours that evening.

Turnbull then chased him around a car for at least 22 minutes and fired a number of shots before shooting Glen in the back - the shot which proved fatal.

“I remember it clear as anything, getting that phone call, ” Alison said.

“He was larger than life.

“He always had a strong opinion on things, and you always knew where you stood. But he was a very caring man, and a great family man.”

Turnbull was sentenced to a "de facto life sentence" of 35 years behind bars for the killing of Glen Turner, after a five-week trial in Sydney last year.

The defence had maintained Turnbull's major depressive disorder was caused by years of tension over illegal land-clearing on the family's properties at Croppa Creek.

The Supreme Court judge presiding over the case, Justice Peter Johnson, said it was clear Turnbull had a hatred of Glen Turner, who he blamed for the OEH attention on his farming properties, telling him when he shot him, "You've ruined the Turnbulls. You are continually persecuting us. The only way you're getting home is in a body bag".

The tragic and heart-wrenching story caught the attention of the nation, throwing open debate on illegal land clearing for agricultural use.

But it’s an issue Alison insists, hangs in balance.

“There’s got to be a balance between farming and the environment,” Alison said.

“There are still people who think the farmer was justified in what he did.

“If Glen had been a police officer trying to shut down a drug dealer, they would have responded (differently), but unfortunately, it’s a very divisive minority.

“Glen loved going out and talking to farmers… you never expect this.”

Sydney-based director Gregory Miller approached Alison and Glen’s sister, Fran Pearce, before the trial, to follow their journey through the courts for a documentary raising awareness of illegal land clearing.

“It was (confronting), but it was a story I think that needed to be told,” Alison said.

“I didn’t really hesitate.

“I got a good feeling about Greg, so I was quite happy to be a part of it.

“I just don’t want people to forget.

“Often after the initial shock and publicity, and the trial, and then it’s over.

“I just want it to always be there.”

The feature documentary, Cultivating Murder, follows the bond forged between Glen’s wife and sister throughout the trial, and the grief shared by family, friends and colleagues of his.

The film also delves into the environmental debate, featuring Tamworth environmental consultant Phil Spark, who carries out his own investigations into illegal land clearing when the government fails to do so.

The story of local woman Alaine Anderson, who is Turnbull’s neighbour and a farmer from the Moree district, is also told as she fights to save koalas and the remnant native habitat in the face of aggressive agricultural development.

Before the trial, Mr Miller filmed interviews “under the radar” with those directly involved in the events.

The film weaves these stories together with the story of the murder and subsequent trial.

Cultivating Murder will make its world premiere at the Capitol Theatre in Tamworth this week.

The question the film asks is, not who did it, but why did he do it?

Outside court after sentencing in June 2016, Turnbull's wife, Robeena avoided media, but son, Grant Turnbull said his father was "coping" with the sentence, but called for the laws around native vegetation to change.

"The frustration that's out there, it's not just my father, there are many people out there in rural NSW that are extremely frustrated, extremely frustrated with the way it is administered and the act itself, it just needs to change," he said at the time.

While he acknowledged this was no basis for murder, he said two families had been torn apart by what happened.

Mr Miller said the film was just as much about bringing to light the issue of land clearing across farming communities as it was about the people affected by Glen’s death.

“People are taking sides on this issue,” Mr Miller said.

“People who have seen this film are very moved by the story.

“I want people to find out what Glen stood for.”

Glen lived on a property just outside of Tamworth with his young family.

Mr Miller chose to premiere the documentary in Glen’s hometown because he was so well-respected across the region.

His wife Alison, Phil Spark, family, friends and colleagues who live and work in the region will attend the Cultivating Murder premiere at the Capitol Theatre on Thursday night at 7pm.

Australian Koala Foundation CEO Deborah Tabart OAM will also attend the screening. 

Alison hopes the film will allow Glen’s legacy to live on.

“It is a story that needs to be told,” Alison said. 

“I just hope people don’t forget (Glen).”

The film will be released nationally on April 20.