A four-year-old boy with head injuries and an 83-year-old man are among 19 people hurt in the incident at Flinders Street on Thursday afternoon.

Twelve victims remain in hospital, down from 19 on Thursday night, including the elderly man who’s believed to be in a critical condition.

The driver, a 32-year-old Australian citizen of Afghan descent, was arrested after being dragged out of the car by an off-duty police sergeant who is having surgery for a hand injury today.

Acting Police Chief Commissioner Shane Patton said while he was yet to be formally interviewed he did make a number “utterances” to investigators on Thursday night.

“He spoke about dreams, he spoke about voices but he also did attribute some of his actions to the poor treatment of Muslims,” Patton told the Nine Network.

Asked if there were links to terrorism, he said: “That’s certainly one area we’re exploring in respect to motivation.”

Patton did say the man was not known to intelligence agencies.

The man will undergo psychiatrically assessment and police hope to formally interview him on Friday afternoon.

Patton said the man was on a mental health plan and was due to attend an appointment on Thursday morning but didn’t show.

More witnesses came forward today, telling how the car raced at up to 100 km/h through pedestrians lined up at a busy crossing which is used by up to 600,000 people during the morning and afternoon peak.

The driver is known to police following a 2010 minor assault matter and has a history of drug use and mental health issues.

The act, deemed “deliberate” by police attack comes 11 months after six people were killed in a similar incident just four blocks away in Bourke Street.

“The only thing that slowed him down was him hitting pedestrians,” witness Jim told ABC TV.

Premier Daniel Andrews condemned the “horrific act, an evil act, an act of cowardice, perpetrated against innocent bystanders” but urged the public to go about their festive activities.

Patton reassured the public hundreds more police would be on the streets over Christmas and New Year.

A second man, 24, who was filming nearby the incident, and had knives in his bag and a small about of cannabis, has been released.

He’s expected to be charged on summons with drugs and weapons possession but the alleged offences are not linked to the Flinders Street incident.

All roads in Melbourne’s CBD reopened about 2am and trams were operating as normal on Friday morning.

Mental health advocacy group beyondblue released a statement this morning pointing out that people who experience mental health conditions are no more violent than other people.

“Criminality should not be confused with mental illness,” the statement said.

“Research consistently shows that people with mental health conditions are more likely to be victims of crime rather than perpetrators.”

– AAP