Families of children killed during the Troubles have condemned those who bombed the Manchester Arena as "insane" for targeting a venue filled with innocent kids.
Twenty-two people, including an eight-year-old girl, were killed and 59 injured when a suicide bomber caused carnage at the end of a concert by American singer Ariana Grande.
During the Troubles 157 children aged 16 and under lost their lives in bombings and shootings.
Victor Barker, whose 12-year-old boy James lost his life in the Real IRA's Omagh bomb in 1998, said he "felt deeply" for the families of those who lost their lives in Manchester, and condemned the suicide bomber for targeting a venue packed with innocent children.
James had been due to go golfing with his father, but instead decided to accompany 12-year-old Spanish exchange student Fernando Blasco Bacelga on a school trip to the Ulster American Folk Park.
On the way back the bus stopped to let the children attend a festival in Omagh, and the youngsters were caught up in the blast.
"I feel for those people so much; the perpetrators of these atrocities are completely mad, they're insane," Mr Barker said.
"How could they possibly think they could achieve anything by killing innocent children? There's a subtle difference between these people and the IRA- the IRA placed the bombs and left; these people are so fanatical that they kill themselves as well.
"It's a mindset that right-minded people can't cope with, and I feel sorry for people who thought they were taking their children to a pop concert to enjoy it and ended up suffering.
"Even those who haven't been killed may have been hurt or have seen things that will affect them.
"It was like that in Omagh - it wasn't just the 29 people who died, other people suffered horrific problems and injuries.
"After the event it's particularly hard for people to move on and find a new purpose without the people who were cruelly taken away - that's the biggest challenge.
"It's very hard to recover and I think of James constantly, at birthdays and Christmas, and on the anniversary on August 15 I go to his grave, as I often do, to remember him. He would have been almost 32 years old now."
Mr Barker says that it is important for the families whose loved ones were caught up in the Manchester attack not to feel guilty.
"The only people who are guilty are those that planted the bomb," he stated.
"For people in that situation, I would say that they have to try and be strong and remember the good memories about their loved ones rather than the bad."
Colin Parry, whose 12-year-old son Tim was fatally injured in the 1993 Warrington bomb, said that the psychological scars of the Manchester bombing victims would take as long to heal as the physical scars.
"Those people will have thought that their kids were as safe as houses. I saw a photo of an eight-year-old girl who was killed, she was beautiful and her life has been snuffed out," he said.
"The families will be beyond devastated and bewildered; they wouldn't have expected this in a million years.
"It could scar them, perhaps for life. They may learn to live with it, but they will never forget what happened."
Mr Parry, who along with his wife Wendy set up the Tim Parry Johnathan Ball Foundation for Peace to support those affected by terrorism and violent conflict, said his family now tries to concentrate on the good memories.
"Tim would have been 37 in September and we don't focus on losing him, we focus on the fun and joy he brought to the family. We do think what might have been, what he might have done. He was a ray of sunshine," he added.
Another young victim of the Troubles was 15-year-old Geraldine O'Reilly, who was killed in a chip shop in Belturbet, Co Cavan, on December 28, 1972 after a loyalist car bomb exploded.
Her brother Anthony, who was waiting for her outside, said that seeing young girls affected by the Manchester bomb had brought back memories for him.
"Geraldine was only a child, she was the youngest in our family of eight and our parents never got over her death," he said.
"Like those youngsters at the concert, we felt safe that night. I was very close to her, I doted on her.
"Geraldine wanted to be a teacher and she would have been 60 now. She probably would have been married, with a family of her own."