The ex-partner of Leigh Wallace had attended relationship counselling with her only hours before he fatally shot her in the head.
Flint Wallace, 57, pleaded guilty to murdering Leigh Wallace via audio visual link at Hamilton High Court this morning.
Wallace and Leigh Wallace, 50, who were also first cousins, had been in an on and off again relationship since 2014, according to the summary of facts.
Wallace had a history of family harm incidents and in June last year had his firearms licence revoked.
In July this year Leigh Wallace moved out of the Wallace's Otorohanga property to live with family in Whakatane, but returned to Otorohanga on August 31 to attend relationship counselling.
The pair drove in a Nissan ute to the counselling session together and left at 12.15pm.
Their ute was spotted parked outside a farm in Te Kuiti for four hours and at 5.30pm Wallace was seen hopping back in the vehicle before they both drove back to his Otorohanga home.
Once back at the property, Wallace was sitting in the driver's seat when he fired a rifle at Leigh Wallace, who was sitting beside him, hitting her in the head.
Wallace then called a family member and told him he "had done something stupid".
Family members arrived within 15 minutes to find blood coming from the grandmother's mouth. They grabbed the gun off Wallace.
When police arrived and asked Wallace if he had shot his partner, he nodded. He was unable to speak to police because of his injury.
Emergency services arrived and confirmed Leigh Wallace was dead.
Wallace is due to be sentenced on December 13.