Like any child would have done, seven-year-old Howard Kakita wanted to get a good view of the fearsome B-29 bombers flying overhead.
So 80 years ago today, in the Japanese city of Hiroshima, he climbed onto the roof of his grandparents' house with his brother and peered into the sky.
Moments later, the bomb that changed the world - dropped from the plane called Enola Gay - detonated less than a mile away.
Somehow though, Mr Kakita, now 87, survived the nuclear blast, along with his brother and both grandparents, whom he and his sibling had been visiting from their home in America.
Speaking today to mark the anniversary of the disaster, Mr Kakita revealed the seconds leading up to the explosion, and told how he was knocked out 'instantaneously' by its force.
The non-proliferation campaigner explained to BBC Radio 4's Today Programme that he and his brother had been given a stern warning by their grandmother that likely saved their lives.
'Fortunately for us, our grandmother who was washing dishes in the kitchen, heard a commotion in the roof, ran out and told us to get off the roof in no uncertain terms, and reluctantly we came down,' he said.
'I went into a bath house, a separate structure apart from the house where we took bath.
Howard Kakita, now 87, was seven-and-a-half when the United States dropped an atom bomb on the Japanese city of Hiroshima. He told the BBC how he survived
Mr Kakita (right) with his grandfather and brother Kenny on their return to Hiroshima weeks after the blast. All had lost their hair through radiation poisoning
'And for some reason, I went in there, not sure exactly what the reason was, but that is when the bomb exploded.
'Since we were so close, we were only eight tenths of a mile, 1.3 kilometres from Ground Zero, I didn't notice the flash, nor hear the boom.
'I was knocked out instantaneously. I have no recollection of the blast taking place.'
The bomb, which was the equivalent to the destructive force of 15,000 tonnes of TNT, killed an estimated 80,000 people instantly.
The target that the US crew led by Colonel Paul Tibbets Junior were aiming for was the Aioi Bridge.
But the bomb landed 800feet away from that, instead striking above the Shima Surgical Hospital.
Nearly everything within the surrounding square mile was obliterated. But Mr Kakita, his brother and paternal grandparents all survived.
After the detonation, a huge mushroom cloud (pictured) rose into the sky
The devastating attack on the city on August 6, 1945, killed 80,000 people instantly
Everything within an immediate square mile was obliterated by the blast
The survivor previously recounted his story and shared images of himself with historian Iain MacGregor, the author of the Hiroshima Tapes.
He went on: 'When I came to, a number of minutes later, I'm not sure how long I was out, the structure that I was in was on top of me, I could smell smoke.
'I wasn't seriously injured, so I was able to dig myself out. And I went into the courtyard of our home, where I located my brother.
'He had a slight radiation burn on his forehead, and my grandfather was, with the help of other men, trying to dig my grandmother who was in the kitchen.
'She was buried under the structure there. And she was standing next to a window when the blast took place.
'The shards of glass from the window embedded in her body, and she was bleeding pretty badly when they dug her out.'
However, all four ultimately survived the blast.
The ground crew of the Enola Gay, which was captained by Colonel Paul W. Tibbets Junior (centre)
Survivors of the Hiroshima blast are seen lying in a tent relief center on the banks of the Ota River in the city, on August 7, 1945
A photo taken of Mr Kakita, his grandfather and brother on their return to Hiroshima after the end of the war shows how, despite escaping with their lives, they had all lost their hair from radiation poisoning.
Mr Kakita's maternal grandparents were less lucky.
The body of his grandmother on his mother's side was never found, and her husband - his grandfather - died a month after the blast from head injuries.
Mr Kakita and his brother were not able to return to their parents in America until 1948.
Because of their Japanese heritage, their mother and father were interned in a prison camp in the US for the duration of the war.
They moved to Los Angeles following their release.
Mr Kakita now devotes his time to campaigning for an end to the stockpiling of nuclear weapons.
