A 15-year-old boy driving erratically has sparked a major security incident in Melbourne's CBD, after bystanders screamed at police to shoot him because they feared he was planning to run down pedestrians.
One man said the boy, from Knoxfield in Melbourne's east, drove directly at him and "dead set tried to kill me" outside busy Flinders Street Station on grand final day.
But police said the teenager — who was wearing a helmet and allegedly armed with a weapon — was believed to have a history of mental health issues.
He had no known terrorism links and probably did not pose a great threat, police said.
Video of the incident showed the car being reversed at high speed along Swanston St.
Bystanders called police when they saw the boy, wearing a backpack and carrying a large implement, walking in circles at the intersection of Flinders and Swanston streets after getting out of the car about 8:00am.
Several police officers approached the teenager and tasered him, while others kicked away the implement.
Bystanders were heard yelling, "Shoot him, shoot him".
The Victoria Police critical incident squad and bomb squad were deployed to the scene.
Police earlier said the boy was being assessed in hospital, but later said he was in police custody.
'He tried to run me over'
Jolon Cooke said he was helping to set up grand final equipment in Federation Square when the teenager drove at him.
"He swerved and tried to run me over," Mr Cooke said.
"He dead set tried to kill me.
"He came out of the car with a black baton, full head-to-toe black military gear, took a backpack out of the car to simulate a bomb and then he was telling the cops to come for him."
Victoria Police Acting Superintendent Wayne Newman said officers were treating it as a mental health incident and there were no links to terrorism.
The teenager was taken to hospital to be assessed.
"We believe he has a [history] of mental health [problems]," Acting Superintendent Newman said.
"Because of the actual time of the morning, I don't think it there was a lot of pedestrian traffic fortunately.
"I don't think he posed a great threat."
'He looked like a terrorist'
Witness Jason Smith said the car, which had a red P-plate, was going up and down the street doing skids and burnouts.
"He was all in black with a black helmet and a black backpack, looked like a terrorist," he said.
"Then someone threw a pushbike at him — that was crazy.
"Then the cops eventually got up close and went out of view a bit so they tasered him then that was it.
We were hiding behind the wall for safety in case there was an explosion and it was really, my heart rate … as soon as I saw him all in black, [it was] just scary as," Mr Smith said.
Acting Superintendent Newman said they had no information the boy was trying to harm anyone.
"He was driving certainly erratically which is concerning to Victoria Police and the community but there is no intention, that I'm aware of, that he was deliberately trying to hurt anyone," he said.
"Obviously it was concerning but this paraphernalia he had is freely available, the clothing [is] certainly from any army disposal store but obviously [being] in the CBD dressed like that is of concern.
"But I think that's clearly in line with his mental health condition, which we're assessing."
Acting Superintendent Newman said police had "full capability" available to handle the incident and officers were on the scene within minutes and able to "neutralise the threat from escalating."
"We don't encourage members of the community to engage with that [sort of incident]," he said.
"I think what it shows is that the community have a heightened sense of vigilance in relation to that and certainly Victorians won't stand by idly and let these things occur."