SYDNEY, Australia — The police said four people were shot and killed on Tuesday in Darwin, the capital of Australia’s Northern Territory, when a gunman went on a shooting spree in the city’s main business district.

The Northern Territory police said at least one additional person had been wounded, and that a 45-year-old man had been arrested within an hour of shots being fired. The man had been on parole, the police said.

The authorities said the shooting was not an act of terrorism. A video showed three officers in military camouflage subduing the man.

“We’re still trying to establish the intent and motivation behind this, but all I can say, sadly, is that people have lost their lives this evening,” Reece Kershaw, the Northern Territory police commissioner, said at a news conference in Darwin.