The incident is believed to be linked to a stabbing that took place early this morning involving parties known to one another
Three people are dead and at least 20 people have been injured after a car hit pedestrians in Australia's second-largest city of Melbourne.
Police said the car was deliberately driven into city centre crowds just before 2pm on Friday, local time.
Footage from a witness showed a maroon car driving in circles in an intersection outside Flinders Street railway station with the driver hanging his arm out the window.
The man then drove up the pedestrian section of Bourke Street mall, deliberately hitting people, police said.
One of those killed was a young child.
Ambulance Victoria said that several of those being treated had serious injuries and Royal Children's Hospital said in a statement that they were treating four children from the scene.
Acting Commander Stuart Bateson said the situation was now "contained" and a man has been arrested.
Police confirmed in a statement that they had shot the man before he was taken into custody.
He is being treated for non-life threatening injuries.
Mr Bateson said that the incident is not believed to have been terror-related - and police were in pursuit of the vehicle when it "deliberately struck a number of pedestrians".
A police statement added: "(We) understand the incident is linked to a stabbing that took place in Windsor early this morning involving parties known to one another.
"Following this incident, it is alleged the same man took a woman, who is known to him, hostage in his car. She managed to escape from the car on the Bolte Bridge earlier today."
According to Mr Bateson, there is no further threat to the public.
Rebecca Russo told Australian news outlet Fairfax that she had seen three people hit by a maroon car as it came speeding up the pedestrian-only stretch of Bourke Street Mall.
"We were just standing on Bourke Street, and we heard a bit of a crash coming from the Mall.
"I saw a maroon car driving up the pedestrian path on the Flinders Street side.
"People were running out of the way, they were going very very fast. I saw him hit a few people.
"I saw bodies flying into the air."
Another witness told Sky News Australia: "There was just all this noise and mayhem and then all of a sudden police flying everywhere and just bodies lying all over the ground."
Witness Maria Kitjapanon told The Age newspaper that the car was rammed by a police car, and police fired shots into the car before pulling the driver out.
She said: "There were probably 10 police surrounding that guy's car, with guns drawn, and they fired into the car.
"Then they dragged someone out via the passengers side, then all 10 of them sat on top of him."
Former Victorian police commissioner Christine Nixon told ABC Radio Melbourne that the car missed her by a metre and then, amid the confusion, she returned to the job she knew.
"I just stood there for 15 or 20 minutes directing traffic. No one disobeyed my instructions," she said.