The CCTV video emerged on Tuesday night of a police officer throwing nine punches to the head, neck and back of a Sudanese-born Melbourne man at a Preston chemist, The Age reports.
The vision also shows an officer kneeling on the 23-year-old before he is kicked in the head and hit with a baton then stomped on his back, with the vision showing four officers in total.
The man, who was having a psychotic episode, had reportedly been trying to rob the chemist when a civilian restrained him at the back of the store before police took over in February 2016.
The Victoria Police's Professional Standards Unit found the actions of the police were appropriate and they were in accordance with the law, according to the ABC.
Assistant Commissioner Luke Cornelius said on Tuesday he was very concerned by the security footage obtained by The Age and shared with the ABC.
It was not police practice to stand down officers when a complaint was made, he said.
Any decision regarding the officers would follow the outcome of the Independent Broad-based Anti-corruption Commission's investigation.
Following the footage, legal groups will stand on the steps of the Victorian parliament to call on the state government to overhaul Victoria Police's complaints system, with revelations of police brutality.
It comes as Victoria's anti-corruption commission moves to investigate a group of police officers caught on camera pinning down and beating a Melbourne disability pensioner in September before spraying him with capsicum spray at his home in Preston - which was caught on CCTV.
Premier Daniel Andrews said on Tuesday he had not watched the footage of the incident at the pensioner's home.
"Victoria Police, as the nation's best police force, conduct themselves with professionalism and are in my experience proportionate to the risks that they face," he said.
Opposition Leader Matthew Guy labelled John's case "abhorrent" saying it highlighted the need for a better police complaints system as "all Victorians will be outraged by it".
Last week's IBAC report found Victoria Police failed to adequately manage conflicts of interests, consider human rights and examine relevant evidence in serious incidents when people were hurt or killed.
