Tears rolled down the face of Tommassino Magliocco as he honoured his father who was murdered in a car bomb attack 37 years ago.
The Italian man laid a wreath in the capital to mark the anniversary of the Dublin and Monaghan bombings as the Queen made her first historic visit to the Republic.
Antonio Magliocco was just 37 when he was killed in the atrocity, leaving behind his wife and three young children under four.
"You will never forget a family member but on this occasion, coming here, it's more emotional," said Mr Magliocco, the eldest child, who returned to Dublin for the anniversary.
"But we want answers. We want to know why and we want to know who was involved. We want to know the truth."
Thirty four men, women and children - including an unborn baby - were killed in the series of no-warning car bombs across Dublin and Monaghan on May 17 1974.
The atrocities were the greatest loss of life in a single day of the Troubles.
About 200 people, including bereaved families, survivors of the blasts and politicians, united in grief at a memorial on Talbot Street in Dublin's north inner city to remember the dead in a simple service.
Campaign group Justice For the Forgotten - which believes the explosions were carried out by loyalist paramilitaries with British state collusion - also made a fresh appeal for the Queen to urge Prime Minister David Cameron to open secret files which were withheld during an inquiry.
Margaret Urwin, spokeswoman, said the truth would slot in the final piece of the jigsaw.
"Proportionate to our day, this was Ireland's 9/11," she said.
"Would anyone dare to suggest that any anniversary of 9/11 should be overlooked? I don't think so."
Bernie McNally, chairman, was just 16 when she was seriously injured in one of the bombs and lost her sight in her right eye.
The mother and grandmother said she struggled to live a normal life for years after witnessing firemen carrying bodies from shops, thinking they were mannequins.
But she looked on the Queen's visit as a fantastic opportunity for the truth to come out to build relations between Ireland and Britain.
"She's a mother, she's a grandmother and she's 80 odd years of age," said Mrs McNally.
"I'm sure she thinks about the legacy she will be leaving for her children and grandchildren and the people of England.
"I just hope as a human being that she shows a warmer more humane side and that it will trigger something in her."