Mr Finlay, who is chief executive of children’s charity Barnardos, said the young boy had found the letter beside his father’s body.
“I have been haunted for the last five years by the opening lines of the letter. It said: ‘Son you are the head of the family now’,” said Mr Finlay.
“And two years after that boy found that letter, he was still struggling to come to terms with the burden that it placed upon his shoulders.
“He was still trying to figure out what it was that he had done that sent his father away and what he could have done differently to keep his father with him.”
Mr Finlay was speaking at a conference at the Royal Hospital Kilmainham in Dublin yesterday to mark World Suicide Prevention Day.
The conference was organised by Console, a support organisation for those bereaved by suicide.
Mr Finlay said Barnardos offered bereavement counselling for children.
“About a quarter of those children have lost parents, usually a young father, through suicide,” he said.
Children and adults bereaved by suicide felt burdened because there was no explanation for what happened to people they loved.
“They blame themselves because nobody can explain why it happened.
“I hope this is not a macabre image but every seat in this hall a year ago could have been occupied by somebody who is not here today,” he pointed out.
Last year, 527 people died by suicide in Ireland, a 24% increase on the previous year.
Health Minister Mary Harney said Minister of State with responsibility for mental health John Moloney would begin holding a series of meetings in every major town in the country in a bid to end the stigma of mental illness.
And, she said, despite the challenging economic times, resources in the area of suicide prevention would continue to be prioritised.
Dr Harry Barry, a GP with a long standing interest in mental health, who addressed the conference, said he was keen to point out the effect stress could have on a young man’s brain.
“If a young man becomes anxious or depressed, the emotional side of his brain takes over and swamps his logical side, leaving them more vulnerable to suicide,” he warned.
“We really need to launch a public campaign to get the message across to young men that it is cool to talk about their feelings.”