WARNING: Graphic video

HORRIFYING CCTV footage has captured the moment a man drove an SUV into a crowd of people at a busy Melbourne intersection.

At least 19 people were injured when a white car driven by a 32-year-old with a history of drug use and mental illness mounted a tram track and accelerated into pedestrians outside bustling Flinders St Station.

The man was released from hospital on Friday afternoon and is now in police custody and set to be interviewed.

Video captured by nearby security cameras shows the Suzuki Grand Vitara pull out from a street park and head towards a large crowd of people crossing the street.

The car appears to accelerate as it approaches the crossing pedestrians and continues to charge through the crowds striking innocent people in its path.

The crowd can be seen to disperse as bodies are flung onto the road after apparently being hit by the large vehicle.

Witnesses at the scene described seeing bodies flying “like dolls” after being hit.

Police are treating the shocking incident as a “deliberate act”.

They say the Australian citizen of Afghan descent, named as Saeed Noori by the Herald Sun, was driving alone when he crashed a white Suzuki Grand Vitara into pedestrians at high speed outside Flinders St Station on Thursday at 4.41pm.

He is under police guard in St Vincent’s Hospital as police continue their “fluid investigation”.

Speaking on Thursday, Victoria Police acting chief commissioner Shane Patton said the driver was known to police for “historical assault matters” but was not on bail. He is still to undergo psychiatric assessment and is yet to be formally interviewed.

MORE: Witnesses describe hearing ‘bang, bang, bang’

Mr Patton said the man had a “history of drug use as well as mental health issues”.

“We understand that he is on a mental health plan and receiving treatment for a mental illness,” he said. “We’re working to clarify that.”

The incident is not being treated as a terror investigation “at this time”, despite being supported by counter-terrorism teams. Mr Patton said police believed it was “quarantined to a singular incident” rather than part of a larger plot.

“It’s horrendous and life-changing for all emergency services who attend,” he said. “It’s life changing for victims and for those present. Their lives will be changed forever.”

All roads in Melbourne’s central business district were reopened about 2am Friday and trams are now operating as usual.

The crime scene on Flinders St has been cleared, but a heavy police presence remains this morning.

‘ACT OF EVIL AND COWARDICE’

Nineteen people were injured in the seconds of chaos, including a four-year-old boy who is believed to have a head injury. They range from four to 83 years old, with some ages still unknown.

Twelve people are still receiving treatment in hospital and one, a man in his 80s, is in a critical condition.

The 32-year-old driver and another 24-year-old man were arrested at the scene. The 24-year-old was seen filming the incident on his phone and found to be carrying a bag containing knives.

Police said the 24-year-old had been released early Friday morning and that he was expected to be charged with possession of cannabis and a prohibited weapon.

The offences were not linked to the Flinders St incident, police said.

Victorian Premier Daniel Andrews slammed the “act of evil” but praised an off-duty policeman who detained the driver.

“He [the off-duty officer] deserves special praise for the way in which he instinctively came to the rescue of others avoiding so much further carnage.”

MORE: Hero cop praised for quick thinking

Extensive footage posted online shows a man in a white shirt and blue jeans being dragged from the passenger side of the vehicle while others lie on the ground around it. Smoke pours out of the bonnet of the car.

Footage filmed by one eyewitness showed police kneeling over a man in a white T-shirt and checking his pulse immediately after the incident.

One witness told the Herald Sun police were “knocking” the driver and “trying to wake up him up”.

“He was pulled out of the car with a gun at his chest, like the big one (large gun) ... they dragged him out ... he looked unconscious,” he said.

Man handcuffed at the scene of Flinders Street incident Man handcuffed at the scene of Flinders Street incident

Prime Minister Malcolm Turnbull sent his “thoughts and prayers” to the victims and the emergency services workers tending to them.

The shocking event came nearly three years on from the Sydney siege, which occurred on December 15, 2014, and about 11 months after another man drove a Holden Commodore down Bourke St, killing six.

Thursday’s incident coincided with a reported gas bottle explosion at Frankston Bayside shopping centre, which police treated as unrelated.

‘PEOPLE FLYING EVERYWHERE’

A four-year-old boy with head injuries was transported to Royal Children’s Hospital in a serious condition after the incident. Other victims were taken to the Royal Melbourne and Alfred Hospital, with some treated in the street.

Witnesses described horrific scenes that included “people flying everywhere” as the carnage unfolded at the corner of Elizabeth and Flinders streets during rush hour.

The vehicle ran a red light just after 4.30pm, witnesses told local radio station 3AW, before mowing down pedestrians. Bystanders said the vehicle made “no effort to slow down”.

Sue, of Walker’s Doughnuts, said: “We could hear this noise, as we looked left, we saw this white car. It just mauled everybody down. People are flying everywhere. We heard thump, thump. People are running everywhere.”

Witness Jim said the Suzuki was travelling west along Flinders St up to 100km/h.

“The intersection was full of pedestrians and he just ploughed through,” he told ABC TV. “The only thing that slowed him down was him hitting pedestrians.

“There was no braking, there was no slowing down. Whether it was targeted or whether he had a heart attack, or was drunk, I don’t know.”

Lauren Lopatko tweeted: “Something just happened outside Elizabeth St tram stop outside Flinders St station. Avoid area if you can. I saw ppl screaming & smoke.”

Reddit user TheElderGodsSmile added: “Sister in law said ... he knocked them over like skittles. Bloody awful.”

Fright_ posted: “Saw grown men and women crying on Platform 1 of Flinders St station. Overheard phone conversation mentioning car hitting people. Seems like I got there a few mins after it happened. Elizabeth St entrance to Flinders is closed. That big intersection being blocked off by police about 15 mins ago. Heaps of emergency services there now.”

Elton Hindoli, who works in the area, said a man who was pulled from the car appeared to be unconscious.

“A girl came into the shop and she was very upset,” he said. “It wasn’t clear if the driver was hitting them on purpose or not. It sounded like the man who they took out of the car was not awake.”

Lachlan Read said the whole incident lasted about 15 seconds.

“He has gone straight through the red light at pace and it was bang, bang, bang. It was just one after the other. The last bang the car stopped,” the 20-year-old said.

“There were bodies on the ground and people running up to them — it was mayhem.”

Vince was working in a shop at Flinders St Station and rushed to the scene before emergency services arrived.

“There was no screaming, just people lying there,” he told AAP, adding that onlookers were quick to lend a hand. “They were just holding them and comforting them.”

Those with video footage or images that may assist police with their investigation are urged to upload it here.

Anyone with information should contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au.