Cameron Paterson resigned from his role as a police custody officer in May 2018, after an internal investigation into his conduct was launched and he was charged with several offences.

He later pleaded guilty and was convicted of nine offences, including possessing an unregistered longarm and unregistered handgun, and doing an act likely to cause an animal pain or suffering.

The charges formed part of the basis of a detective superintendent's decision to hit Paterson with a firearms prohibition order, which are designed to closely monitor people who pose risks to public safety for 10 years.

The animal cruelty charge related to a video Paterson filmed of his dog mauling a kangaroo on a dirt road while, according to a veterinarian, he merely watched on and allowed it to be terrorised.

Paterson said he was not "behaving sadistically" and had accidentally hit the kangaroo with his vehicle.

He went to put the kangaroo out of its misery when his dog shockingly attacked the animal.

"I was incredulous and began filming," he told the Victorian Civil and Administrative Tribunal.

Additionally, the detective superintendent considered Paterson's past behaviour, including other instances of alleged animal cruelty.

A colleague recalled Paterson saying words to the effect that "he wanted to kill something and see blood" - a claim he rejected.

The colleague said Paterson spoke about killing emus and described how one died when he shot it, expressing how excited he was about it.

"I think (that) was the time he talked about blowing the emu's leg off and how funny this was," the tribunal witness said.

Paterson said the story about the emu wasn't true and his counsel argued the animal incidents had nothing to do with firearms.

Animal-related incidents indicated Paterson enjoyed or was entirely detached from depictions and descriptions of pain, senior tribunal member Anna Dea found.

The former police custody officer said he was distressed, not angry, when he fired multiple rounds into a gully below his property after a phone call.

Paterson said he conducted himself appropriately as a police custody officer, contesting claims he did not properly heat inmates' food and said things like "they're just crooks".

The tribunal member found that, despite Paterson's "disgraceful" cruelty to animals and potentially dangerous discharge of a firearm, there was nothing to suggest he was at risk of engaging in firearms-related conduct that would jeopardise public safety.

Therefore, it wasn't in the public interest for the order to be maintained, so Ms Dea ordered it be set aside.

"Some of his other conduct was tasteless in the extreme," she said in a decision published this week.

"Had I been asked to decide whether the applicant was a fit and proper person, I might have had difficulty making a positive finding. However, that has not been my task in this proceeding."

Paterson pointed out logistical issues with the firearms prohibition order, including that he couldn't attend others' properties where he lived rurally and many people had legal guns.

Australian Associated Press