What happened

The streets outside Flinders Street Station were busy with commuters and holiday shoppers when the SUV rammed into pedestrians.

Witnesses told CNN affiliate Seven Network the car was barreling down the road at about 60 miles per hour (100 kph).

"We heard this noise and we looked up, then we just heard bang, bang, bang, and people flying everywhere," said Jim Stoupas, who owns a doughnut shop nearby.

"We had a lot of customers in our shop and they were traumatized."

The man was taken into custody by an off-duty police officer after resisting arrest, Patton said. Both the man and the police officer were injured in the scuffle.

Another man detained

Police detained a 24-year-old man who was filming the incident on his phone, and found three knives in his bag.

"We don't yet have any relationship established between the 24-year-old man and the driver. In fact, there may be no relationship between them," Patton said.

Flinders Street is one of Melbourne's busiest pedestrian roads, running between a major train station and the bustling city center. This week, it's crowded with commuters and shoppers making last-minute holiday purchases.

Police said several of those injured were in critical condition, and a pre-school age child who was hospitalized with a head injury is in serious condition, Ambulance Victoria said.

Concrete barriers

The streets and landmarks around Melbourne's Flinders Street station have been the target of multiple attempted terrorist plots, all foiled by police within the past year.

Australian authorities described it as "one of the most substantial terrorist plots that have been disrupted over the last several years."