A man pulled two of his children to safety but his desperate attempts to rescue two others were in vain as a fire tore through their family home in Christchurch.
Eight-year-old Brayden and 9-month-old Arianna died in the blaze - with reports Brayden was found near the room of his sister and indications he might have been trying to save her from the inferno.
In an interview with The Press in Christchurch, Brayden's grandmother, Angela Martin, said the children's mother, Nicole Mulligan, had called her in an hysterical state soon after the fire in Vivian St, Burwood on Tuesday night.
"She said to me, 'my babies have died, I'm having a nightmare'."
Nicole's partner Des Cooke, the father of Arianna, had rescued two of the four children in the house but flames and smoke forced him and a neighbour to retreat as they tried to save the other two.
"Des heroically saved the lives of his two other young children and suffered injuries himself after re-entering the burning house in an attempt to save Brayden and Arianna," says a Givealittle page set up for the family.
"Nicole, Des and their two surviving children, 6-year-old Lucas and 2-year-old Brianna, face the reality of losing their children, siblings, home and possessions, all in one night."
Fire and Emergency assistant area commander Mike Bowden told MediaWorks an investigation into how the fire started was under way.
"One child was rescued by firefighters during search and rescue operations. Tragically, this child subsequently passed away. A further deceased child was located in an unsurvivable bedroom."
More than $80,000 in donations have so far come in for the family.
Ashley Looyer has established the Givealittle page to support the family.
"Your donations will help the family of Brayden and Arianna cover funeral costs and help them get back on their feet without the financial burden that will accompany this horrific loss," the page reads.
Many people expressed their condolences on the page, leaving messages of sympathy and love.
One donor said: "No parent should have to endure that horror."
Another said they were "sending strength and love".
NZ Gift of Love and Strength a Christchurch-based charity is taking donations for the family, which can be dropped of at the local Little Explorers Preschool.