Port Arthur massacre: John Howard on how 'unforgettable' day unfolded

As a convict settlement, Port Arthur was said to have been built on misery, crime and brutality.

Twenty-five years ago today Martin Bryant, a heavily-armed killer, changed the site, and the country, forever.

Reflecting on Australia's deadliest mass shooting today, John Howard, the then-newly-elected Prime Minister called it "an unforgettable day for all the wrong reasons".

READ MORE: John Howard reveals his biggest regrets as prime minister

Armed with a semi-automatic rifle, the gunman killed 35 people and left 23 wounded.

For many years, it remained the world's worst mass shooting by a lone gunman in modern history.

At the time of the massacre, Mr Howard had only recently been elected prime minister.

"My press secretary rang me and said 'there's been terrible shooting incident in Tasmania, in Port Arthur, you better turn on the TV,'" Mr Howard told Ben Fordham on 2GB.

The prime minister watched the horror unfolding, and was quickly briefed by Tasmanian Premier Anthony Rundle and the Australian Federal Police.

"It was obvious that this would be an unbelievably tragic moment in the lives of innocent people just going about their daily lives," he said.

Later that day, as the horror of what had happened became clear, John Major, the then-UK prime minister, telephoned Mr Howard from London.

"He spoke … about the massacre in Dunblane in Scotland which had taken 27 lives, and he never imagined he would be consoling an Australian Prime Minister who had seen his country suffer an even greater outrage."

Mr Howard decided to pass major gun reform legislation just 12 days after the shooting.

"Instinctively, I knew I had to do something quite major."

Against fierce opposition from the gun lobby, the Howard Government toughened Australia's gun laws by banning automatic weapons.

He would become the first prime minister to wear a bulletproof vest on Australian soil.

"I should never have worn it," Mr Howard told 9News, more than 20 years after the Port Arthur massacre.

"That was security advice I was given. I never really felt unsafe in Australia.

"I knew there were a lot of people in Australia who disagreed very strongly with what I did.

"That's the stuff of politics. But Australians are not violent people."

The Howard government bought back almost 700,000 guns at a cost of more than $300 million.

Mr Howard told 2GB Australia is now "a much safer country" because of the gun reforms he pushed through.

Bryant remains in Risdon Prison in Hobart, where he is concurrently serving 35 life sentences without the possibility of parole.