Two of the children, aged 4 and 6, were carried to safety by armed police moments after the man was shot dead.
Their mother, who was jailed for three years in March on methamphetamine charges, found out about the shooting from her cell mate, she told Stuff.
Both children were rushed to an ambulance before being taken to Tauranga Hospital with minor injuries.
She claimed her ex-partner kidnapped her and took her to a secluded spot where he beat her unconscious and left her to find her own way home in 2014.
"He was mentally unstable ... nine years of constant physical abuse," she alleged.
"When he kidnapped me where he pretty much beat me and left me out in the middle of nowhere and he drove off, I had no concept of time and I was bloodied."
A neighbour told The Herald the male was "trying to turn his life around".
She told The Herald she used to see the man walking children to school at the same time she did.
Her friend who used to live next door to the man knew him well and he had reached out to her just last week, the neighbour said.
"She said he had previously got out of jail and was trying to turn his life around. She is really devastated at the moment."
The man's ex-partner told Stuff he tried to run over her and her children on a busy Hamilton street after they had tried to escape on foot on her birthday.
"I woke up on my birthday to a knife in my face and him saying get the f*** up bitch," she claimed.
"He dragged my daughter, who was just a baby, he threw her off the bed and pretty much I fought him the whole day and I wrestled the knife off him. It was a whole day of hell."
She told Stuff she later escaped from the man and took a taxi to collect her children and run away from him.
"I grabbed my kids. That's when he nearly killed us, we were all running down the street and we saw his car and he was catching up with us ... we had a head start, he ran us down and he was only inches away from killing us.
After that day, she decided to leave him and keep her children safe, she said.
"... I kept that promise to my children that [their] mum was never going to go back to him and I've always kept them safe. I was just happy to be alive then and that's when I decided that that was enough for my kids."