Murder is not among most children's playground games.
But Philip Dutton, a clinical psychologist who worked with the young survivors of the Dunblane massacre, says traumatised children tend to use games to re-enact the events that haunt them.
"Often, young children will play at killing afterwards," he said. "But they don't tell the adults, because they don't want to upset them, just as adults don't want to mention it and upset the children.
"There's a fear that they only got some of us this time, so they'll come back and get the rest. But, with work, they can get their sense of safety back."
On March 13, 1996, Thomas Hamilton walked into the gym at Dunblane primary, near the Scottish city of Stirling, carrying four handguns. He shot a hail of bullets at a class of five and six-year-olds, then aimed through the window of the next-door classroom. where a group of 11-year-olds was sitting down to a maths lesson. Catherine Gordon, their teacher, yelled "hit the ground", an order which saved their lives.
In total, Hamilton fired 105 rounds before turning the gun on himself.
Sixteen of the 28 children in the gym died that day, along with Gwen Mayor, their 47-year-old teacher. It was the worst killing spree of its kind in Britain.
Terrified parents across the country immediately demanded security locks and entry phones on all schools. Schools began to hire doormen, or fit panic alarms.
Dunblane parents and teachers launched the Snowdrop campaign, lobbying for tougher gun laws. They eventually gained a total ban on handguns, and tighter school security. Ten years on, teachers, local authority workers and parents in Dunblane are still unwilling to talk about the shooting.
Some broke their silence for a Five documentary, screened earlier this week, in which PE teacher Eileen Harrild said she had been powerless to stop the gunman. "The gym had a terrible echo anyway, but now it echoed with the close shot of his gun going off," she said. "It was literally a lottery who lived and who died. I've spent a lot of time thinking about why did I survive, when others didn't."
Philip Dutton was among the psychologists called in to help children cope with the aftermath. "You don't have to have post-traumatic stress for something like this to wreck your life," he said. "Some children who have now left school still have daily or weekly thoughts about these occurrences. Some don't have jobs or don't go out, are agoraphobic. Or they could live in a normal way, but small things make them jump, trigger them off."
A car going past quickly, for example, could trigger disproportionate fear.
Survivors might experience flashbacks, or sleep uneasily. Such long-term anxiety could lead to full-scale depression.
"Bereavement and trauma are rolled into one," said Mr Dutton. "And there will be a level of guilt as well. It's not logical, but it is emotional.
You carry that guilt with you, so you can't move on. It's hard to lose that without assistance."
Hass Yilmaz, principal educational psychologist for Brighton and Hove, works with the South of England critical incident group, which responds to trauma in schools. He says that events such as school-based violence, suicide or road accidents can affect children in different ways.
"It's a balance between the trauma, on one hand, and internal resources, on the other," he said. "These resources can include self-esteem, self-confidence, family, religious leaders and therapists. If a person has strong internal resources, they can probably cope. If their resources are on the low side, then a relatively small trauma could tip them over."
Both psychologists advocate therapy for all involved in school-based trauma. But it is also important for teachers to offer a balanced response when discussing the event.
Michael Hughesman, who provides post-traumatic psychological support to schools, said: "Children suddenly realise that something bad can happen and can happen close to home.
"So we need to strike a balance between giving sound, practical advice, and worrying them about what may possibly happen, but probably won't."
Pupils also require a sense of safety and continuity. Mr Hughesman believes that a speedy return to normality is vital but maintaining this illusion of normalcy can be taxing for teachers.
Mr Yilmaz said: "Teachers are holding themselves together for the kids, but heads are holding themselves together for the kids and the staff. They're the ones dealing with the publicity, the media and the local authority. It can be isolated at the top. We need to be sensitive to that."