The young boy who escaped his mother's clutches as she allegedly tried to kill him might have survived because of his self defence skills.
The mother has been charged with murder over the alleged drowning of the boy's five-year-old brother.
The boys' father, who can't be named for legal reasons, told news.com.au his surviving nine-year-old son swallowed lots of water when his mother allegedly pushed him under water in the Murray River, near Moama in southern New South Wales, last Thursday.
"He went under the water, so water went onto his lungs," his father said.
The boy managed to break free and run away before a dog attacked him and his mother.
But it was too late for the youngest boy, whose body was found in the river by police divers, on Saturday. The boys' 27-year-old mother, who also can't be named for legal reasons, was today charged with murder of the little boy. Outside court, the woman's lawyer Peter Hebbard said his client was remorseful, the Herald Sun reported.
"The words she used to me was 'I would never hurt my children, I do not know what happened'," he said.
"She knows that something's happened and she knows she's done something."
She was last week charged with attempted murder of the nine-year-old. A court heard on Friday the mother "had to drown my babies".
The eldest son was still in intensive care today but was expected to make a full physical recovery, according to his father. The boy has reportedly had two operations to treat the dog bites. His father has not had any contact with his son since the attack but said he has been talking to friends and family who have.
"The dog bit him on the legs, torso, the stomach and back," his father said.
"He has to go in for a few more operations and skin grafts."
He said doctors and family members told him his son "sort of knows what's happened but it's still a blur for him".
"All my support is going to that poor kid now," he said.
The boy's father is not a legal guardian of the child and last saw him about five years ago.
"When I was in his life he'd come out with little sayings all the time, humorous little lines like 'bow chicka wow wow'," he said.
"He does karate, self defence... that's how (I suspect) he managed (to survive)."
He never met his youngest son and will no longer have the chance.
"I'll never see my five-year-old," he said. "No Christmases, birthdays or sport activities. No day-to-day general father or parent duties."
The boys' parents hadn't had contact with each other for years but the father said the 27-year-old was once a good mother.
"She was charming, nice and caring at the start," he said.
"If (our son) wanted something to eat, he'd ask and she'd get it."
The father told news.com.au he "had no idea anything like this (would happen)".
He said the pair dated on and off for a total of about eight months over several years.
"(We split) six weeks before (our first son) was born then got back together after and tried to reconcile for him," he said.
"When we were having arguments she turned into something totally different."
Like many tragedies, there are often more questions than answers.
"The million dollar question is 'why'?" the father said.
"I'm very doubtful I'll ever get the answer.
"But to know what she was thinking at the time would be good for closure.
"I'm trying to wrap my head around it."
But according to the father others had noticed changes in the mother over recent years.
"I applied with (the authorities) for them to be with their grandparents 18 months ago when I found out (there were problems)," he said.
"I was hoping that would lead to me being able to see the children.
"But the system failed my kids."
The father said he first learned about the tragedy when he was contacted by a family member around 9am on Thursday.
"Since then I've had six to nine hours sleep in three to four days," he said.
His only hope now is to reconnect with his surviving son.
"I'm still trying to get information from her side of the family about the boys in general: how they've been, what they've done," he said.
"I'm trying to fill in for lost time."