The animal was usually a gentle dog and the owner, Andrew Palhares, was "totally surprised" by what occurred.

The dog teamed up with a Jack Russell on March 25 last year.

The pair killed 12 sheep and left a further 19 with "horrific" injuries that led to them being put down.

There were 14 more sheep which were injured but were able to be treated.

Some of the attacked sheep were covered in blood and had their stomachs ripped open, with some of the injured animals in extreme pain.

The sheep's owner, who lived next door to Palhares' parents on Huon Creek Road in Wodonga, shot both dogs.

It's still unclear who owned the Jack Russell, but a microchip traced the German Shepherd back to Palhares.

Lawyer Mario Vaccaro told the Wodonga Magistrates Court this week it was an incident that couldn't be predicted.

"I'm told this dog was at all times very gentle," he said.

"The Jack Russell, I don't know who owns it.

"No one knows who owns it.

"I suppose (they) become like a type of pack."

Mr Vaccaro said Palhares was "totally surprised by what happened ... the female German Shepherd was a gentle dog".

The loss to the victim was $7051 for the Merino ewes and further costs for vet fees.

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Wodonga Council team leader compliance Craig McClanahan said dog attacks resulting in death were considered the most serious of animal incidents.

"Council takes a serious view in relation to dog attacks," he said.

Palhares doesn't have any priors.

Magistrate Peter Mithen said the case should serve as a warning for all pet owners to be vigilant.

"Good people who own dogs can have these things happen," he said.

"It's a terrific thing to own a dog but when it does something like this, the reverse feeling is devastation."

Palhares was placed on a 12-month good behaviour bond without conviction.

The victim will be compensated about $8000.