On Thursday, a 27-year-old woman allegedly drowned her five-year-old son and tried to drown his nine-year-old brother.

It has been alleged in court that she first attempted to drown the older boy, who managed to break free when his mother was distracted by her younger child’s terrified screams.

As he returned to the riverbank, the older brother was allegedly mauled by Buddy, a pitbull-cross that lived at a nearby property. The older boy was airlifted to Melbourne's Royal Children's Hospital, where he remains in a stable condition.

Jess Smith, believed to be one of Buddy’s owners, started a petition to save the dog, which was seized by authorities after the incident, freed.

And in a ray of positive news amid the bleak tragedy, NSW Police late on Monday advised Murray River Council the animal was responding to “extreme circumstances” and acting in a “reasonable defence”, meaning it would not be put down.

The dog had earlier been seized following a council order.

“Buddy the dog has reacted and attempted to save the boys,” Ms Smith wrote on the petition.

“In doing so he has bit the eldest boy in his rescue attempts (and) unfortunately he was unable to save the youngest boy.

“He has since been seized from his owners who are distraught by not only what this mother has (allegedly) done but also that our dog has been seized when he should be labelled a hero instead.”

Pit bulls have long been considered a dangerous dog and are banned in many parts of the world, including NSW, but restrictions around cross-breeds are less clear.

Wagga vet Jack Killalea said in general pitbulls were known to be aggressive dogs.

“You do hear of some dogs doing amazing things, but they’re the breeds that are known for search and rescue and helping people,” Mr Killalea said. “Staffys and pitbulls are the cause of 90 per cent of dog attacks. In certain situations dogs can interpret distress – but I’m being purely speculative here – this sounds like dominant behaviour.”

However, Ms Smith claimed Buddy didn’t have a history of being dangerous and had never bitten anyone.

“He has clearly seen a child in distress and attempted to help.”