A man with a history of mental health and drug abuse issues has driven into a street crowded with pedestrians in Melbourne, killing at least four people, including a child, and injuring around 15 others.
The incident began in the early afternoon when a man was seen driving in erratic circles in the middle of a major junction in the centre of Australia's second-largest city.
The driver then turned on to the Bourke Street Mall, a pedestrian-only road, mowing people down before continuing on to a pavement and hitting several others, Victoria state Police Acting Commander Stuart Bateson said.
Police shot the driver and arrested him at the scene. The 26-year-old is being treated in hospital for non-life-threatening injuries. Officials have not released his name and said there is no further threat to the public.
The incident came amid global concern over extremists using vehicles to strike crowds, following truck attacks in Berlin and Nice last year. Police Chief Commissioner Graham Ashton said the Melbourne incident had no link to terrorism.
The driver has a history of mental health and drug abuse issues, and has an extensive record of domestic violence, Mr Ashton told reporters. Last weekend, he was arrested after police said he assaulted members of his family.
Before he began his rampage through Melbourne, police say he was involved in a domestic stabbing incident in a suburb earlier on Friday.
Police tried to intercept his vehicle, but called off the chase before he entered the central area because he was driving so erratically. Mr Ashton said officers feared a chase through the city might endanger the community.
Two adults and a child died after being struck by the car, Mr Ashton said, and a fourth person died in a hospital on Friday night. Police did not release any details of that victim.
Another 15 people were injured, with five in critical condition, including an infant.
Sharn Baylis, a tourist from the southern city of Adelaide, said she was on Bourke Street when she mistook the car for an unmarked police vehicle before it started slamming into pedestrians.
"He was just collecting people as he was going along and they were flying like skittles, basically," she told the Australian Broadcasting Corp. "He was just driving in a really determined fashion, just in a straight line. There was no hesitancy as he got to the crowds and he didn't swerve, it was just - he just drove through them."
Video shot from a news helicopter showed several officers standing over a man lying on the pavement, wearing only underwear, his hands apparently handcuffed behind his back.
A video posted on social media captured the moment the car began driving in circles in the junction before continuing towards Bourke Street. The driver could be seen hanging out the window, apparently shouting.
The crisis unfolded at a particularly busy time in Melbourne, which is hosting the Australian Open tennis championship. Officials said the event was continuing as normal.