Gordon Jenkins says he killed a dog after it attacked his wife.
The 58-year-old walked 120m from his Takaka home to the home of Heather Cole, who was looking after the border collie, and left with the dog - he says at Ms Cole's request. She could not be contacted.
Once home he claims he took a knife from the kitchen and killed the dog.
"I did my best, I've never killed anything in my life."
He then called police, who took the dog's body and later charged him with wilful ill-treatment of an animal. He will appear in the Nelson District Court next month.
About eight hours before the dog's death, Mr Jenkins' wife Teresa was attacked by the dog while talking to Ms Cole, who did not own the dog but was caring for it, Mr Jenkins said. The dog lunged at his wife twice, tearing a "softball-sized chunk" from her leg and leaving deep puncture wounds and bruising to her buttocks and thigh.
The mother-of-three remains in Hutt Hospital, where she has undergone skin grafts. A cast on her leg is due to be removed this week.
Mr Jenkins told the New Zealand Herald this morning he had never been in trouble with the law before.
He blamed police for not removing the dog immediately, and said he killed it because he was afraid someone else would be attacked.
"I didn't want that on my conscience. I don't want anymore damage done from that animal."
He had thought about whether the dog suffered, but was adamant he "did the best I could". He remained in Takaka because he was "broke" and could not afford to travel to Wellington.
The invalid beneficiary has cancer, depression and other ailments and is permanently on morphine.
It wasn't easy being away from his wife of 24 years, he said.
"I'm missing her like hell."
Mrs Jenkins could not be contacted this morning, but told Fairfax she supported her husband's killing of the dog.
She still faced the risk of infection after skin grafts, which could lead to gangrene and cause her to lose her leg, Mr Jenkins said.
"That's still on her mind and everybody's worried about a b****y dog."
Nelson Senior Sergeant Blair Hall said animal control was called after the attack, but could not comment further as Mr Jenkins had been charged.
Animals had the right to go through a due process to determine their fate, Mr Hall said.
"If they are required to be destroyed, by law it has to be done in a humane way without suffering."
Police were also investigating possible liability on the part of the person in possession of the dog at the time of the incident.