
The slaughter of 35 innocent people in Tasmania back in 1996 is still as vivid as ever for those linked to the Port Arthur massacre.

The bloody rampage carried out by Martin Bryant exactly 20 years ago stunned Australia and was acknowledged as the world's worst massacre at the time.

Today, April 28, 2016, marks two decades since the then 28-year-old drove a yellow Volvo to Port Arthur armed with a sports bag full of ammunition and a military-style semi-automatic rifle.

Some 500 people gathered at the Port Arthur Historic Site for the official memorial service on Thursday to mark 20 years since the massacre.

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The bloody rampage at Port Arthur carried out by Martin Bryant exactly 20 years ago on April 28 stunned Australia and was acknowledged as the world's worst massacre at the time

Today, April 28, 2016, marks two decades since Bryant drove a yellow Volvo to Port Arthur armed with a sports bag full of ammunition and a military-style semi-automatic rifle

Bryant, who was unemployed and described as a loner by those who knew him, had driven to the Seascape Guesthouse on April 28, 1996 where he murdered owners David and Sally Martin to begin his bloody rampage.

He then headed to Port Arthur historic site where he had lunch before opening fire on tourists and locals, including children. Bryant hunted down victims as he moved through the cafe, gift shop and carpark.

Carolyn Loughton was shot in the back while her 15-year-old daughter Sarah was shot in the head and killed.

'It was just this immense explosion,' Ms Loughton told SBS of the moment the shooting started.

'I'm seeing bits of the walls coming away and then I saw him with this massive, massive gun up shooting people.'

Countless survivors have told how they played dead on the floor as the gunman stalked his victims.

Countless survivors have told how they played dead on the floor as Bryant stalked his victims

Some 500 people, including Prime Minister Malcolm Turnbull and his wife Lucy, gathered at the Port Arthur Historic Site for the official memorial service on Thursday to mark 20 years since the massacre

He then headed to Port Arthur historic site where he opened fire on tourists and locals, including children. He hunted down victims as he moved through the cafe, gift shop and carpark. This aerial view of crime scene shows the bodies of victims on the ground

Bryant took a hostage and drove back to the Seascape Guesthouse where he had earlier murdered the owners. Bryant stayed inside for 18 hours until it caught fire and he had to run out covered in flames

Local woman Nanette Mikac had been visiting the historic site that day with daughters Alannah, six, and Madeline, three.

As the shootings took place the young mother instinctively led her girls along a road leading away from the site. Thinking she must have almost made it to safety, Bryant's yellow Volvo had come along.

The gunman had stepped from his car before shooting dead Ms Mikac and then each of her daughters.

A short time later he shot and killed the four occupants of a car arriving at the historic site, before stealing their BMW.

More people would die and a man was taken hostage as Bryant made his way back to the guesthouse, where he was holed up for 18 hours.

His trail of destruction took the lives of 35 tourists and locals, some children, and injured another 23.

Bryant pleaded guilty to 72 charges including murder, attempted murder, causing grievous bodily harm and arson. He was ordered to serve 35 life sentences without parole on November 22, 1996

Bryant took the lives of 35 locals and tourists, and injured another 23 during the bloody rampage on April 28

Armed police at the scene in Port Arthur where Bryant shot dead 35 innocent people

Bryant has never offered an explanation for his actions, but there is speculation, including from investigators, that his murders were sparked out of retribution for grievances, and other victims were collateral damage

Bryant, who was unemployed and described as a loner by those who knew him, had driven to the Seascape Guesthouse where he murdered owners David and Sally Martin to begin his bloody rampage

Byrant murdered Sally and David Martin at their Seascape bed and breakfast property before he headed to Port Arthur

Special ops police from Melbourne had called for a bulldozer to lead their planned raid of the bed and breakfast property where Bryant was holed up.

But the heavy machinery wasn't needed as he was forced out after 18 hours by a fire. He was screaming with his clothes alight as he was taken into custody and to hospital for treatment.

Months of police questioning followed. Footage of those interviews, recently aired by the Seven Network, showed Bryant initially denying any knowledge of the killings, although he did admit a kidnapping that day.

But Bryant finally pleaded guilty to 72 charges including murder, attempted murder, causing grievous bodily harm and arson.

On November 22, 1996, more than seven months after the massacre, Tasmanian Supreme Court Chief Justice William Cox ordered Bryant serve 35 life sentences without parole.

Then-prime minister John Howard used the massacre to gather support for tighter gun laws, which passed parliament.

Bryant has never offered an explanation for his actions, but there is speculation, including from investigators, that his murders were sparked out of retribution for grievances and others were collateral damage.

He will die at Hobart's Risdon Prison.

Nanette Mikac, pictured with her husband Walter, was shot dead by Bryant alongside her two daughters Alannah, six, and Madeline, three

Medical staff at Hobart Hospital were inundated with casualties after Bryant opened fire

Bryant finally pleaded guilty to 72 charges including murder, attempted murder, causing grievous bodily harm and arson

Bryant was ordered to serve 35 life sentences, which means will die in Hobart's Risdon Prison

An aerial view of the Seascape Guesthouse shows smoke coming from the ruins after Bryant was arrested

Prime Minister Malcolm Turnbull, former PM John Howard and Foreign Minister Julie Bishop were among the 500 people who attended a commemorative service where the shooting unfolded 20 years ago.

'We gather today to remember loved ones lost,' master of ceremonies Edward Gauden said.

'We gather to remember those injured and we gather to remember those who gave so much.'

Port Arthur Historic Site Management Authority chairwoman Sharon Sullivan explained that while there are people who opposed the idea of holding an event for the 20th anniversary, it was important for many people.

'There are some people affected by the tragedy who have come back to Port Arthur for the first time in 20 years,' Professor Sullivan said.

'That is incredibly gratifying for us.

'We also understand there are some people who cannot bear to return and perhaps never will.'

Floral tributes were laid around a memorial pool near the Broad Arrow Cafe where the shooting started 20 years ago and the devastation was greatest.

Survivors, family and friends were tearful as they embraced at the site just behind the former eatery.

Prime Minister Malcolm Turnbull and his wife Lucy were among those to lay a wreath near a cafe where the shooting unfolded 20 years ago

Former prime minister John Howard was accompanied by Foreign Minister Julie Bishop as they laid a wreath at the memorial service. Mr Howard, who was PM at the time, used the massacre to gather support for tighter gun laws, which passed parliament

Prime Minister Malcolm Turnbull was among the 500 people who attended a service where the shooting unfolded 20 years ago

Floral tributes were laid around a memorial pool near the Broad Arrow Cafe where the shooting started 20 years ago and the devastation was greatest