Sisters Nikita and Dominique Hingston were strangled by their father, Frank, who then committed suicide, an inquest has found.
Motueka coroner Jim Fry found that the girls, aged five and six, died by suffocation caused by strangulation on August 4.
Detective John Nicholls told the inquest the girls were found dead bytheir mother, Pauline, on August 4, when she arrived to pick them up after they had stayed the night with their father at his home in Riwaka, 5km from Motueka.
Mr Hingston's body was found in a shed at the rear of the property.
The coroner ruled that his death was caused by asphyxiation by hanging.
Mr Nicholls said Mr Hingston had regular access to his daughters, but Ms Hingston had filed an application for custody, which had upset him.
Mr Hingston had changed his surname from Miranda by deed poll several years earlier, but was not married to Ms Hingston.
The couple had been separated for three weeks.
Mr Nicholls said Mr Hingston had told colleagues he was unhappy and was thinking about suicide.
He had few friends and believed he had no future.
He could not afford to live in the house he was renting but moving into a smaller bach would mean he could not have his daughters to stay.
One colleague said Mr Hingston seemed "obsessed" by his daughters.
Two days before he died, he told a co-worker he was thinking about killing himself, but the thought of what would happen to his daughters stopped him, Mr Nicholls said.
A post-mortem examination had found cannabis in Mr Hingston's blood, consistent with smoking one cigarette, and a small amount of alcohol in a urine sample, but not in a blood sample.
Mr Nicholls said he believed the deaths occurred around midnight on August 4.
Mr Fry said it was impossible to guess what Mr Hingston was thinking before his death, but it seemed that his fear of losing his daughters, feelings of isolation and other pressures had caused him to become "paranoid and selfish".
Ms Hingston had shown great courage and strength of character following the deaths, in being able to deal with police and media.
"Nothing in this world could have prepared the mother of these two girls for this event."
