The first thing Michael Sweeney did when he learnt his wife Madeline had died in the attack on the World Trade Centre was to tell their two children.
Anna is five years old, Jack just three – criminally young to be robbed of their mother, an attendant on the hijacked American Airlines Flight 11, which was flown into the north tower. But Mr Sweeney felt there was no option. At his home in Acton, Massachusetts, he gently called his son and daughter to him and told them that their mother would not be coming home.
"He did it as soon as he heard. They were struck by the trauma of the events," the children's grandfather, Robert Sweeney said. "But children are resilient. They bounce back quicker than adults."
Or so everyone hopes. As President George Bush yesterday symbolically raised the Stars and Stripes that has been flying at half-mast at Camp David, attention turned to a group who have perhaps suffered more than any as a result of the attacks on America – the children of those who died.
No one has yet done the numbers. No one has yet calculated accurately just how many children were orphaned, or lost a mother, a father or an aunt or uncle who brought them up as their own.
But the rough estimates are staggering. Just from the bond-trading firm, Cantor Fitzgerald – which was housed on four floors at the top of the World Trade Centre's north tower – there are believed to be 1,500 children who have lost a parent.
"We have never been faced with anything of this magnitude simultaneously," Ruth Kreitzman, a clinical social worker with the Jewish Board of Family and Children's Services, told The New York Times.
"Even people who have dealt with bereaved kids a lot are struggling to understand now how this will be interpreted by children."
The organisation is just one of many children's charities in the US which are realising how the scale of their work is going to increase in the weeks, months and years ahead. It is not just those children who have been directly bereaved by the loss of a parent or relative who have been traumatised, but also those children whose parents narrowly escaped and have been left feeling scared and vulnerable.
On a wider level, experts say, children across America are likely to feel traumatised every time they see the mesmerising television footage of the terror attacks on New York and Washington.
Ms Kreitzman's organisation has opened a number of emergency drop-in centres in New York where families can go to discuss their fears and concerns. Professional social workers, psychiatrists, and psychologists who have received special training in trauma and its short-term and long-term effects are on hand to offer help. Counsellors say that often the signs of trauma and mourning can take months to reveal themselves.
Yesterday morning, the organisation's vice-president, Dr Alan Siskind, was helping to staff the information helpline at the centre on Manhattan's West 57th Street. "I think we are going to be dealing with the effect of this for years to come," he said. "And I think people are only just beginning to realise that."
It is the scale of those who have been affected that is shocking: so many children whose lives have been irrevocably changed, so many relatives now struggling over what is best for these most innocent victims of the attacks.
Experts point out that the problem is made even more difficult by post-war social trends – from high divorce rates and single motherhood – that have fragmented many families.
One such single parent was Rosa Julia Gonzalez, a 32-year-old woman with a 12-year-old daughter. As the twin towers of the World Trade Centre burst into flames and then started to fall, Ms Gonzalez made one final phone call to ask her sister to take care of her child.
It seems, however, that more men than women died in the attack on New York. Like a previous generation of women whose husbands were called to wear the uniform of their country and never returned from war, these widows face an uncertain future trying to bring up their children without a father and a wage-earner. Many will be forced to sell their homes if they cannot afford to raise their families on benefits or find jobs that pay them enough to live on.
Ironically, the tragedy is most keenly felt by those who tried to help others. Many of the firefighters of New York – more than 300 of whom are thought to have lost their lives – came from traditional Irish Catholic communities with large families. Many who died left five or more children. Hector Tirado Jr, though not from an Irish Catholic background, left five children ranging from six to 11 years old.
"Their sense of loss is palpable," said Mr Tirado's uncle, Robert, one of the relatives now trying to help. "You can just be with them and they're all sad. We try to make them play with each other and other kids, like normal kids, but you cannot avoid it."
The firefighter separated from his wife three years ago, Mr Tirado said. For the five children, his death represents "losing their father twice".
Perhaps inevitably, the loss of so many parents – thousands of whom were in their 20s, 30s or 40s – means that children may grow up not remembering their mothers and fathers.
Michael Cunningham, a Cantor Fitzgerald employee in his 30s who died in the disaster, had just become a father. He had left his two-week-old son and wife at home in New Jersey to return to work after paternity leave.
Two babies whose fathers were lost in the attacks have been born since 11 September.
The new domestic circumstances forced on relatives has also created some ugly and difficult situations.
One victim, Yamel Merino, had told friends she wanted her eight-year-old son, Kevin Villa, to live with his grandmother if anything ever happened to her. But since her death in the attacks, the boy's father has been making threats that he will try to obtain custody.
"I just hope they respect mom's wishes," said a friend of Ms Merino, Maureen Niciu.
It fell to Ms Niciu to break the news of her friend's death to Kevin. She said: "His face just dropped like his whole world had ended."