A NSW environment officer involved in a terrifying standoff with farmer Ian Turnbull that ended with his colleague being shot dead has successfully sued Turnbull's estate for damages.

Robert Strange, an officer at the Office of Environment and Heritage, was threatened with a bullet "in the heart" during the ordeal in which Turnbull killed his colleague Glen Turner with a hunting rifle.

Mr Turner had been investigating Turnbull for illegal clearing of native vegetation and the two men were carrying out what should have been a routine visit of land around Turnbull's property at Croppa Creek, near Moree, in July 2014.

The environment protection officers were standing on public land near Turnbull's property when the farmer used a hunting rifle that he kept in his ute for shooting wild pigs and kangaroos to kill Mr Turner.