The pit bull involved in the Moama drowning tragedy will not be put down after police found the dog was trying to save the nine-year-old boy who survived the ordeal.

The dog "Buddy" was seized by Murray River Council on Thursday at the request of police after it mauled the nine-year-old boy in the shallows of the Murray River.

The boy had survived an attempted drowning, allegedly at the hands of his mother, before he was confronted by the dog.

Buddy allegedly mauled the boy, and his mother.

It is alleged the nine-year-old boy managed to struggle free from his mother in the river, before she drowned her five-year-old son.

The 27-year-old woman, who cannot be identified for legal reasons, has been charged with murder and attempted murder.

The surviving nine-year-old boy was flown to Melbourne's Royal Children's Hospital, where he has since had surgery.

Buddy was seized by the council on police orders, leaving his owners fearing he would be destroyed.

On Monday, however, police advised the council they believed the pit bull cross was acting to protect the young boy.

"The NSW Police have since advised us that their investigations to date have deemed that the dog in question was responding to extreme circumstances," Murray River Council interim general manager Margot Stork said.

"It is likely that the dog was acting in reasonable defence of the nine-year-old boy.

"The NSW Police have advised council that they will not be seeking an order to destroy this animal."

It follows a significant public campaign to save Buddy from being destroyed, including a plea from the nine-year-old boy's grandfather.

"I own a similar dog, and I know he was trying to save the boys, it's their nature when they are raised with kids," the grandfather said.

"Let the ones who his actions affected decide. I have one grandson left, because this brave dog took action as required."

An online petition to "Help save Buddy", which was created on March 4, gathered more than 40,000 signatures in two days.

The nine-year-old boy's condition improved on Monday morning, with a hospital spokeswoman saying he was in a stable condition.

Multiple members of the community expressed concerns about the dog's welfare after the attack last week.

But Buddy's owners insisted the dog "reacted and attempted to save the boys [and] in doing so he has bit the eldest boy in his rescue attempts".

"Our dog has been seized when he should be labelled a hero instead," the owners said in a post on the petition website.

"Buddy is a member of our family and has grown up around children his whole life and has been the most gentlest dog, he has clearly seen a child in distress and attempted to help.

"Dogs don't have hands to help like us humans they have to use their teeth and in doing so it's being portrayed as this dog has attacked the young boy."

- The Age