For the many affected, the wounds are still raw 20 years on.

Marking the anniversary this month will bring back a flood of memories and emotions, but a leading trauma specialist says it can be truly healing if those affected are allowed to make meaning of it.

Clinical psychologist Dr Rob Gordon was brought into Tasmania in 1996 to help begin healing a community that was torn apart by the horrific acts of a lone gunman. 

Dr Gordon coordinated counselling services and support networks for survivors and emergency service workers.

He returned to the Tasman Peninsula last month to help the community cope with the upcoming anniversary.

Dr Gordon’s experience helps many people affected by disasters to understand their reactions to trauma and grief.

He has worked on recovery programs for the Bali bombings, the 2004 tsunami, the Christchurch earthquake, Victorian bushfires and Tasmania’s Dunalley fires.

The Port Arthur massacre is the worst trauma he’s worked on, he says.

Hundreds will gather at the Port Arthur historic site on April 28 to remember the 35 people slain.

Former prime minister John Howard, who changed the nation’s gun laws, will attend along with many other dignitaries, families of those lost and local community members.

The event will gain national and international attention.

Dr Gordon hosted an intimate counselling session at a Port Arthur function centre in March at the request of a neighbourhood group.

Surrounded by a mass of tranquil gum trees, metallic blue water and a dearth of tourist buses it’s hard to imagine the death that surrounded the area in 1996.

A group of locals gathered to hear Dr Gordon speak – some who were there on that fateful day in April.

His message to them was that talking about their feelings and making meaning of them was very important.

"Recovering from an event like this is really a life-long process,” he tells the group.

One man in the group cautiously chimes in that he still finds it too difficult to talk about.

“I just find that if I talk about it I get too emotional,” he says.

A community leader asks how she should approach talking to local people about their feelings in the lead up to the anniversary.

"If people avoid it, they can never put it in the past,” Dr Gordon says.

"If we can help people reflect on and talk about the traumatic event that doesn't evoke more pain, then in the course of that talking ... it starts to recede into the past.

“It’s very meaningful to be sad and remember – the pain of that grief is very important in resolving things.”

He said empathy was better than sympathy.

“We only want our nearest and dearest to sympathise – we want everyone else to empathise.”

The Victorian psychologist was based in the coordination centre in Hobart during the aftermath of the massacre, but he also held community meetings in Port Arthur.

“We wanted to help people understand that this huge thing has happened and they need to feel a part of the community,” he said.

“The first thing we did was give people a sense that there is now a community of those affected.

“It was very hard to draw people into that because their instinct is to just flee and get away.”

Dr Gordon said people experiencing trauma will find that the people they usually relied on for support can’t understand what they’ve gone through or how to help them.

“They will often get misguided advice that doesn’t work,” he said.

“They’ll often become, even within their own family, very isolated.”

He said finding a recovery community was the key to healing.

“When it’s human intent versus natural forces, the level of trauma is always higher,” he said.

“A lot of people will be traumatised because they were in a place where someone was running around trying to kill people, so the spread of the trauma is higher.

“And that involves the violation of the fundamental belief in human decency.”

Dr Gordon said marking the twentieth anniversary will be healing for people if they can make sense and meaning of their feelings.

“The important thing is that what re-traumatises people is re-exposure to the images and the emotion of the time,” he said.

“What heals people is making meaning and sense of it.

“You can’t make meaning of images and emotions unless you convert them into language and you develop a story about them.”

He said recently released footage of police interviews from the investigation and scenes from the massacre were like “opening wounds”.

"If anniversary events don’t involve representing all the raw images and the footage from the time but speak about this as a historical event and help people understand what it’s meant for their lives and how their lives have unfolded since then and perhaps even what they’ve learnt from it – this helps to let it sink into the past as an element of history,” he said.

Dr Gordon said those affected by the anniversary should mark it in a way they feel comfortable.

The service at the site is open to the public and will be held at 12.30pm on April 28, and a service will be held at St David’s Cathedral at the same time.