The killer of Ariana Eva Mahu thought he was a god saving his iwi from a makutu (curse) when he stabbed her at a Tauranga Marae.

Mahu died after being stabbed in an unprovoked attack while she was helping in the wharekai on February 23. Her killer, Tamati Mason, has been found not guilty by reasons on insanity in the High Court at Rotorua on August 13.

Justice Lang said both the prosecution and defence-appointed psychiatrists reached the same conclusion that Mason was suffering from schizophrenia and mental illness and unaware of the morality of his actions.

Reports prepared by the psychiatrists paint a grim picture of Mason's mental state.

"He was convinced he needed to stab and kill the victim, otherwise she would destroy his family and his iwi," the report read.

"He believed the victim entered into a conspiracy with the police and the Government to blackmail and for financial gain.

"He believed he was a god to his people, a tohunga, and was receiving messages from his tupuna. He believed he had clairvoyant powers..."

The report also said Mason said he was relieved by his actions and said anyone else would have done the same. The reported concluded Mason had an insanity defence to his actions.

"In my opinion he was unable to understand the moral wrongfulness of his actions having regard to the commonly held standards of right and wrong," the report said.

Mahu was described as a caring and loving mother by her family and her tragic loss has had devastating effects on her whanau.

"She was loved by all," her friend Karen Whaiapu said. "She would do anything for everyone."

"She cared for Tamati like he was her own."

Whaiapu was in the wharekai at Huria Marae when Mason approached Mahu with a knife and proceeded to stab her in and around her neck.

"I still see the smug look on his face," she said. "The look in his eyes when he put the knife down as if to say, 'I got you'."

Mahu's oldest son, Te Reihana Robbie Johvanga Pokene, was asleep inside the wharenui when his mother was attacked.

An uncle woke him up at 1am and drove him to Tuaranga Hospital where he learned she had been killed.

"Seeing my mum in a cold dark room with one light on I looked at her and knew she wasn't getting up again," he said.

"Since my mum was murdered I feel I'm angry all the time. I wanted to hurt everybody all around me. Killing my mum has made me someone else.

"You have made my life a living hell."

Pokene said his mum treated Mason like a son and helped feed him whenever he was unable to work.

"You used and abused us," he said.

"She felt sorry for you and you used her to get what you needed."

Justice Lang said Mason was a danger to the community and he therefore had to be detained as a special patient in the custody of the Department of Health.

Mason will remain a special patient until he is deemed no longer a risk to himself or others.

The public galley was packed with people from both sides of the family and shared in a karakia and waita as the court case began and ended.

Mason's family hope to reconcile with Mahu's as the two try to come to terms with the killing.

- Stuff.co.nz