John installed a CCTV system at his house in Melbourne's northern suburbs after it was burgled a few years back.

It was supposed to capture robbers — not police.

But the video it recorded in October 2017 shows a number of Victoria Police officers dragging the disability pensioner into his front yard, where he is pinned to the ground.

One officer repeatedly beats John across the lower legs.

"I thought I was going to die," John told 7.30.

John was ill and distressed, withdrawing from the pain medication he has been on since his back surgery.

He has anxiety and depression and his health carers called emergency services, concerned by his deteriorating mental state.

He also has a minor assault on his police record from 10 years ago.

Police dispatch notes warned that John may confront police and attempt to provoke them into shooting him.

'Open the door, John'

Sorry, this video has expired Capsicum spray is used on John when he opens the front door and when he's pinned down on the ground.

From behind his locked screen door John repeatedly pleaded with police to leave him alone.

But police threatened to break down the door.

When John did open the door police allege he came at them with two raised fists.

But the video shows him appearing to try to fend off an officer approaching him with a canister of capsicum spray.

Moments later, he was pinned to the ground by the police. One sprayed him with the capsicum centimetres from his face.

There was a watering can nearby that could have been used to wash off the capsicum spray.

Instead, one of the officers got the garden hose and aimed it at John's face at maximum pressure.

"He's aiming for my nostrils and it's going into my lungs — and that's when I started choking from the water and from the hot mace going into my respiratory [system]," he said.

"I couldn't breathe.

"I really, literally, thought I was going to drown.

"You can feel the mace and the water together in your lungs."

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'It was like a game for them'

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 37 seconds 37 s A police officer appears to use his phone to capture another officer spraying water into John's face.

The video shows one of the policemen smiling as he pulls his phone out and appears to capture the moment the officer aims the jet of water into John's eyes for a third time.

"It was like a game for them. They wanted to get their rocks off, you know?" John said.

"It's wrong."

None of the six officers present that day raised concerns about their colleagues' behaviour in the police notes of the incident.

But John won't be complaining. At least, not to police.

He has no faith that police will investigate it fairly.

Instead, he has taken his case to the state's Independent Broad-based Anti-Corruption Commission (IBAC), and is also launching a civil case.

Assistant Commissioner Luke Cornelius , the acting head of Professional Standards Command at Victoria Police, said he was "very concerned" after seeing the vision for the first time last week.

"The conduct displayed on the CCTV demanded examination and explanation. The members involved clearly needed to be called to account for their conduct," he said.

He said he ordered an investigation after viewing the video but was later advised IBAC had begun its own inquiry, which takes the lead.

Assistant Commissioner Cornelius said he was unable to comment any further on the incident "because doing so may generate the perception that I might be seeking to influence IBAC or pre-judge the outcomes of their investigation".

Sorry, this video has expired Victoria Police explain why officers caught beating a pensioner on CCTV haven't been stood down

He said the officers had not been stood down.

"Our practice is that we conduct an initial inquiry and if, on advice from the investigators undertaking that inquiry they recommend that members ought be stood down, then that decision is considered at that time," he said.

Premier Daniel Andrews said he had not seen the video, and would not comment on the specific incident, but said he was grateful to Victoria Police for the work they did.

"I am not diminishing any individual incident or the merit of any individual complaint, but in a broader sense I think Victorians can have confidence in Victoria Police," Mr Andrews said.

"However if there are complaints to make, then people can come forward and make them and they will be investigated properly."

Opposition Leader Matthew Guy said every Victorian would be "horrified" by the vision.

"No-one is above the law, that footage and that report is exceedingly disturbing and I hope that there is appropriate action that follows up from it," he told ABC Radio Melbourne.

Police Association secretary Wayne Gatt said it was too early to say if the officers should be stood down.

After 20 years of policing, Mr Gatt said he had learned there were always two sides to a story.

"It's absolutely essential that those officers involved have the opportunity to put their case forward, to explain the circumstances and provide as much about the background of that situation as they can before we speculate what it was or what it wasn't," he said.

"The right and proper approach is to have a thorough, proper, investigation where everybody's given the opportunity to put their case forward then recommendations can be made on the basis of all of that evidence."

People worried about police investigating their own

Lawyer, Jeremy King, has heard many stories similar to John's. ( ABC News )

John's lawyer, Jeremy King, has litigated multiple cases of alleged police misconduct and brutality.

He said the police complaint process in Victoria was failing.

"I've been doing this work for a long time, and you hear many, many stories from people about the way that police have acted," he said.

"What John's case highlights is that these things do occur, and he obviously has the evidence to be able to back it up.

"For him to be treated in that way is humiliating and quite degrading for someone who has mental health issues and had committed no crime."

The video, obtained by The Age, comes as Victoria's police complaints system is in crisis.

In 2015, IBAC found fewer than 10 per cent of complaints to regional police stations were upheld.

When the allegations involved police brutality, the figure dropped to just 4 per cent.

The following year, IBAC urged Victoria Police to overhaul its internal complaint system because it was failing to weed out repeat offenders.

Last week IBAC produced another report criticising the way police handle internal investigations of serious incidents — including failing to consider relevant evidence and giving too much weight to police testimony over that of independent witnesses.

In February, Victoria Police Assistant Commissioner Brett Guerin quit in disgrace as the head of Professional Standards after it was revealed he had used a fake identity to post racist rants online.

Victoria Police said it had zero tolerance for poor behaviour within its ranks and it was "strongly supportive" of the current parliamentary inquiry examining the way police misconduct is investigated.

Mr King says it's not surprising people have little confidence in the system.

"A lot of the time, people don't want to complain directly to the police because they're worried about the inherent conflict in police investigating their own," he said.

"But then the problem is they complain to IBAC, and IBAC refers over 90 per cent of those back to the police to complain, which is extraordinarily disheartening for people who have thought they've gone to an independent body, they're going to get some sort of independent oversight, and then it just goes back to the police who are then investigating their own."

'Why are you doing this to me?'

John sitting on his front step. ( ABC News: Chris Gillett )

When it was over, the video shows John sitting on the grass crying.

"Why are you doing this to me?" he asked.

The lead police officer offered his explanation and some of the other six officers laughed.

"Are you happy? Are you happy?" the officer questioned.

John groaned.

"I'm a disabled pensioner. That's how tough you are," John said.

"You came out and tried to take a swing at me," the lead cop countered.

"What the f**k did you think would happen? It was the only way it was going to go down."

Read the written statement from Victoria Police.