After a night in custody, Thompson, 25, pleaded guilty to four counts of animal cruelty which led to the grisly deaths of nine out of 11 puppies.

He cannot now own, acquire, buy or possess any animal, or even be around another animal without an adult present, for a decade.

The order, made in East Maitland local court by magistrate Caleb Franklin, led to the removal by the RSPCA hours later of a pregnant dog named Sasha from the home Thompson shares with his girlfriend Sarah.

Thompson, 25, was arrested by police and the RSPCA on Thursday night after a plea for public assistance resulted in an outpouring of emotion on social media.

Police say the bull terrier-cross puppies were first advertised for sale online by their owner Tony Brown last Thursday, March 5. Almost a week later when they had not sold, Mr Brown asked Thompson to "get rid of them", but said he did not mean for him to kill them.

The puppies were loaded into Thompson's car about 4.30pm on Wednesday, and he took them to bushland on McLeods Road, Kurri Kurri.

He began killing them with a rock, hitting them in the head and throwing them into the bush. A witness, out walking his own two dogs, confronted Thompson who drove off with five of the puppies still alive.

The RSPCA was called and inspector Scott Meyers arrived to find five dead puppies in the scrub, and two hanging on to life. They were taken to the Rutherford RSPCA veterinary clinic but one died on the way.

Thompson has told police he later destroyed four of the five remaining puppies while the fifth was re-homed.

Duty solicitor David Fleming told the court Thompson's juvenile record was "not good", but he would be seeking an intensive corrections order rather than full-time custody, and that mental health and substance abuse issues would be raised on sentence.

The maximum penalty for animal cruelty under the NSW Crimes Act is five years' imprisonment.

At home after being released on bail, Thompson said he knew it seemed "cold-blooded" but he thought he was doing a friend a favour.

"People are looking at me like I'm a cold-blooded killer because of what I have done and I can understand that," he said.

But he "loved his dog" and was devastated to have her confiscated.

RSPCA NSW Chief Inspector David O'Shannessy said there was no doubt it was one of the worst instances of animal cruelty the RSPCA had dealt with.

Of the 15,000 complaints made to the RSPCA every year, most had to do with an omission, where someone had failed to feed their dog properly or provide veterinary assistance.

"This is a far more significant situation where there is an element of pre-planning and a deliberate attack on the animals," he said.

Rutherford-based RSPCA veterinarian Julian Suchowersky said the surviving pup, a female nicknamed Lucky, had rather serious head injuries but all its vital signs were stable and the pup had improved significantly from when it first came into the clinic.

"She's definitely stable today and we are keeping her on pain relief and trying to keep her as quiet as possible at this stage," he said.

While the clinic had received offers to re-home Lucky, clinic staff were focused on the pup's recovery and were "not thinking too far ahead".

Thompson is due back in court for his sentencing on April 28.

The Newcastle Herald