In this image made from video, Australian police apprehend a man suspected of fatally shooting four people June 4 in Darwin, Australia. (Australian Broadcasting Corporation/AP)

A gunman killed at least four people Tuesday in northern Australia, a rare mass shooting in a nation of strict gun laws. Police arrested a 45-year-old man in the rampage.

Northern Territory Police Commissioner Reece Kershaw told reporters that four men were slain and a woman was wounded when the shooter opened fire at five sites in the city of Darwin. The suspect was identified as a former prison inmate who was paroled in January and was wearing an electronic monitoring bracelet.

The Australian Broadcasting Corp. reported that the gunman fired a sawed-off shotgun at the Palms Motel in the Darwin suburb of Woolner in the late afternoon.

Witnesses said the shooter opened fire in a number of rooms in the motel before fleeing. Police said that they arrested the suspect about an hour later and that he apparently acted alone, the BBC reported.

The city center was locked down for an hour after the shootings.

Prime Minister Scott Morrison told reporters that the attack was not linked to terrorism. Speaking in London during a visit to participate in D-Day commemorations, Morrison called the mass shooting “a terrible act of violence” but said there was “nothing to suggest” that it was “a terrorist act,” the Associated Press reported.

The ABC said police responded to several crime scenes linked to the gunman in Darwin, the capital of Australia’s Northern Territory. A reporter for the broadcaster said she saw police tackle the suspect at a busy intersection and use a stun gun to subdue him.

Kershaw said the suspect was “well-known to police” but did not immediately identify him or offer any information about a motive. Nor did the police commissioner say why the man had been in prison, the AP reported.

It was the worst mass killing in Australia since September, when five people were fatally stabbed or beaten in a house near Perth in western Australia. 

Mass shootings have been relatively rare in Australia since it enacted a strict gun-control law after 35 people were killed in a rampage in Port Arthur, Tasmania, in 1996.

In March, a gunman attacked two mosques in Christchurch, New Zealand, killing 51 people in a massacre that prompted the government there to ban most semiautomatic firearms in the country. An Australian anti-Muslim extremist was arrested in Christchurch shortly after those shootings and charged with multiple counts of murder.

Whereas Australians strongly approved of their country’s gun laws even before the Christchurch attacks, opinion polls suggest that the Christchurch shooting rampage has generated support for tougher measures, even though Australia already has some of the world’s strictest gun-control laws. The shooting in Darwin could spark a new debate over legislative changes.

Far-right politicians have repeatedly sought to undermine Australia’s gun laws. In March, Al Jazeera published footage of a sting operation by some of the network’s journalists, who had recorded senior politicians with the far-right One Nation party appearing to seek up to $20 million in donations from the National Rifle Association (NRA), the U.S. gun rights group, during a trip to Washington.

In return, the party officials promised, they would seek to undermine Australia’s tough gun laws. Al Jazeera said the recordings were made in September.

When the recordings were released days after the Christchurch attacks, one of the filmed officials — Steve Dickson, then Queensland’s One Nation leader — denied the allegations, though he acknowledged that meetings had taken place.

Public responses to the recordings indicated that he and other far-right politicians would have a hard time selling their proposed changes to the Australian public. Australian commentators expressed outrage over the NRA’s apparent interest in influencing public opinion abroad through financial or ideological support, which has also been documented in other countries, including Brazil and Canada.

Morrison, a conservative,was among the top officials who defended his country’s tough gun-control laws. He accused One Nation of trying to “sell Australia’s gun laws to the highest bidders, to a foreign buyer.”

“I find that abhorrent,” Morrison said.