MARCH is a sombre, reflective month for many people in the town of Dunblane. It couldn't be otherwise. Next Sunday is the 20th anniversary of the catastrophic events of March 1996, when Thomas Hamilton's murderous impulses led him to shoot dead 16 young children and their teacher. For years afterwards, the killings were what many people thought of whenever the town was mentioned. In more recent times, however, the vibrant successes of Andy Murray have given Dunblane something else to be known for. The town, you suspect, is eternally grateful.

This is a close-knit, self-reliant sort of place. As one man said in the High Street last week: "I think that helped in the end, really. We sort of came closer together", after the shootings. An experienced local counsellor said: “I have over the years heard many moving stories about how families and friends supported each other. I know that in one street the women arranged to meet up and that led to a book club that has continued to meet once a month and is still going strong.”

Mike Robbins is the Provost of Stirling, and helps represent the Dunblane/Bridge of Allan ward on Stirling Council. Twenty years ago, he was the chairman of the Dunblane primary school board. "Very reflective" is the phrase he uses about his feelings at this time of year.

Dunblane, he observes, is a "small, friendly, self-contained community, a place where people naturally pass the time of day when they meet in the street. [In the weeks after the tragedy] people would talk to each other more readily, and you could see people giving each other a hug in the street."

By its very nature as a dormitory town, he adds, "there has been quite a change in the population in the intervening period." People who had moved into Dunblane in that time "clearly have an awareness of what the town went through, and the people I have met have treated the matter with sensitivity and dignity, which is always something that is good to see."

Emphasising that he was speaking purely for himself, Robbins continues: "One thing I tend to find difficult is this expression that people use, 'moving on' – because, really, do you move on? It implies you have left something behind.

"It's one of those things you don't leave behind. It's omnipresent, always part of your life. People say time is a great healer, but it is definitely still there, for me at least. How you cope with that is the difficult thing."

He mentions the memorial stained-glass windows in the town's Holy Family Church. The church, financed by landowners, the Stirlings of Keir, welcomed its first worshippers in December 1934. The windows were unveiled in December 1998, Canon Basil O'Sullivan having already remarked of them: "We hope it will be part of the healing process and that we will have left behind us for the future generations, a monument that is appropriate to the tragedy."

Their theme is the triumph of good over evil. "As far as I'm concerned," says Robbins, "they're an eloquent expression of Faith, how people cope with things and move one step at a time. It's summed up in these three windows, which talk about moving from darkness into light. The message is very powerful, very moving."

The children are also remembered in personalised snowdrop etchings on the windows of the Dunblane Centre, which was built with funds donated in the wake of the incident. In 2014, a book marking its first decade spoke of the "courage and dignity" which with the community has rebuilt and grown "through an enduring emotional struggle."

When news of the killings began to filter out of Dunblane into a disbelieving wider world, Charles Figley was at Manchester Airport. One of the globe's foremost experts on post-traumatic stress disorder, Prof Figley, who was then attached to Florida State University, was awaiting a flight to Edinburgh, where he was to address a workshop. He wept for the lost children and their families. “In all my years working,” he said at the time, “I have never encountered a worse traumatic event … I have worked in some very difficult situations. This one overwhelmed me.”

Today, Prof Figley is based in New Orleans, holder of the Paul Henry Kurzweg MD Distinguished Chair and Professorship at Tulane University’s School of Social Work, and director of the university’s Traumatology Institute. “I arrived in Edinburgh the morning after the tragedy,” he says. “I saw all the newspapers with the headlines of the Dunblane school shooting and the class photograph.

"It was shocking. I veered from my planned schedule to encourage the audience to speak up about their multitude of feelings. All of the observations were then weaved into the training. I recall a rather short, sixty-year-old, graying male therapist among those in attendance. Like many others, he spoke candidly and with signs of emotion about how dreadful it was; that it touched his ‘father heart.’ Everyone understood.”

He is not in a position to say how the people of Dunblane are doing now but draws a comparison with other communities across the world, such as Sandy Hook, in Connecticut, where 20 children and six teachers were shot dead in 2012.

“If they are like most of the communities, including Sandy Hook, we all are surprised by their resilience. Fear and dreading are often far worse than the reality. Everyone in Dunblane, I would guess, struggled to carry on after such a shocking event.

"That is the first element: the traumatic experience with violence. Dunblane, like Sandy Hook, had very, very little experience back in 1996. My guess is that they did what they needed to do. Take one day at a time and draw your strength from yourself, your family/friends, and faith in the future. We are, as a social science, finally focusing some of our attention on resilience and away from PTSD.

"All of this is to say that people like those in Dunblane, Sandy Hook, Columbine, and any place where children are murdered, have no choice but to move on," Prof Figley says. "Limping, perhaps, from the losses and the memories of the traumatic circumstances. There is no reason, however, to expect these symptoms to be permanent. Most recognise that living a full and happy life is a testament to the life of those lost; that carrying the thoughts of the joy of life, though cut short, cast a bright light; a sense of inspiration that can give meaning and focus to one’s life. Like any of us, these communities search for understanding and peace while finding and holding on to the memories of their children."

A few minutes' walk away from the Holy Family Church, at the top of the narrow High Street, stands a quietly potent symbol of the 'new' Dunblane. An otherwise ordinary postbox, it was painted gold in celebration of Andy Murray’s victory over Roger Federer in the London 2012 Olympics. It is just down the road from the Cathedral, where Andy and Kim Sears were married last April. Pink ribbons fluttered from the postbox last month when Kim gave birth to a daughter, Sophia. Murray has said of his sporting success: "It's just nice I've been able to do something that the town is proud of."

Three miles up the road, meanwhile, is Cromlix, the hotel he purchased and renovated. He has observed that he was happy to be able to "give something back to the community I grew up in."

He and his brother Jamie were, of course, at the primary school that day in 1996. Andy wept as he recalled the events in a television interview a few years ago. "The only time I get emotional about Jamie and Andy's Wimbledon wins is when I'm in Dunblane," their mother, Judy, told the Radio Times in 2014. "When you've gone through a really dark, tragic time, and then come to a real high. I hope it helps people to feel something really positive about that town … What it definitely does is make you appreciate what you've got."

"I do not believe we ever 'get over' a major trauma," says the local counsellor in Dunblane, who didn't wish to be named.

"We have to find a new normal that incorporates the event. For many years, whenever I told people that I live and work in Dunblane they would straightaway home in on the shooting. Nowadays, when I say where I am from they talk about Andy Murray. I believe that Andy Murray has enabled Dunblane to find a new norm, a new narrative, whilst never forgetting what has happened in the midst of our community."

Mike Robbins smiles as he recalls the police estimate that some 15,000 people turned up to see Murray when he went walkabout in Dunblane after his Wimbledon triumph in September 2012.

"The place was absolutely jumping and Andy walked around and signed so many autographs. The goodwill generated that day was unbelievable, and you often see pictures of him walking up the High Street, even now. That was a strong, positive image of the place, which has been reinforced by the golden postbox as well. People come from all over to have their picture taken with the postbox. Andy's triumphs have been great for him, and great for Dunblane."

The success of the Snowdrop campaign also helped. Dr Mick North, who lost his daughter, Sophie, was a prominent figure in the campaign, which led to a ban on the ownership and sale of most handguns in the UK. "Being successful in our campaign to ban handguns gave all the families involved great comfort," he has said.

Dr North is one of the people interviewed in a remarkably poignant TV documentary to screened on Wednesday. Also featured are Ron Taylor, the headteacher at the time of the killings; Isabel Wilson, whose daughter, Mhairi, died alongside Sophie; and Amy Hutchison, who still bears the scars from Hamilton's bullets. Many of the interviewees have never spoken publicly before. It's an unshowy but deeply felt portrait, not just of that day 20 years ago but also of its impact on those who witnessed it or were bereaved by it. "I think the baggage is always there ... I don't think it is possible after Dunblane to have a life that is completely normal," observes Isabel.

Ron Taylor says that people "have to cope in their own way." At home he has a box of newspaper clippings and his own version of events that day, but he has never opened it. It is, however, "much more difficult to keep the box in my head locked." The event "was so unprecedented and so huge, with so many implications for so many people," he says, "that we really must mark this important anniversary. It's very difficult for people, it's very difficult for the community, and many people might not agree with me, but it's hugely important to help, as best we can, those who survived, and support those who lost."

Stephen Bennett, who produced and directed the documentary, said the aim had been to make it "the defining project, the final chapter in the Dunblane tragedy."

Great lengths were gone to in order to reassure the interviewees. "I think people were taken with the idea that this was the 20th anniversary, that this was [the story of] one hour in one day in one year, 20 years ago. They were all nervous, and understandably so, because they were opening up a door again, but once they said 'yes', in general, despite the nerves they felt on the day, they were all happy to go forward. They have seen the film and are happy with it. What I like about the film personally is that it contains just their voices, plus archive material. There's no presenter or narrator; there's no intrusion, no birdsong, nothing. It's probably the hardest film, the most undiluted film I have ever made.

"When you start a film like this you ask yourself, what you are trying to say by the end of it? In this case I think there is a huge maze surrounding the events of that day. You don't know how you would deal with it. None of us knows. But they found a way through that maze, through a mixture of friendship, love, compassion, empathy and resilience. Alison shows she has that resilience. She says Dunblane is not going away." Alison is the older sister of Joanna Ross, one of Hamilton's victims. To her, fittingly, go the final words in the documentary. March 13, 1996, she says, "is part of history now unfortunately, as well, and it's something that needs to be remembered, so that everyone's aware that we are still here, we are still getting on with our lives and we didn't just fade into the background. We still had to power on, and push on with our lives. It's important that everyone knows we're doing it – we're doing it well."

In a statement this week the Rev Colin Renwick, minister at Dunblane Cathedral, said the tragic events will long be remembered in Dunblane. "There has not been a day since when there has been no remembrance of those lost, injured, bereaved or traumatised. Since that day people have appreciated the support and prayers of others throughout the world, but have also valued being allowed the space to grieve and rebuild with privacy and dignity, with as little media scrutiny as possible."

A week tomorrow, people will gather in all of Dunblane’s churches and the various services will allow those who gather "to remember and to pray for continuing strength and peace."

Of course, the shadow of Hamilton's premeditated act of evil still hangs over the town, and the media's habit of observing anniversaries (of which this article is part) isn't met with universal approval in the town, as evidenced by a robust sentiment expressed by one elderly man on the part of Stirling Road that fords the Allan Water.

In the end, Mike Robbins' words ring so true: that black, black March day 20 years ago is one of those things you don't leave behind. How you cope with it is the difficult part.

Read more: Survivors of Dunblane massacre speak for first time about the attack

Dunblane: Our Story, BBC One Scotland, Wednesday, 9pm.