The elderly runner in the orange vest who became the face of the Boston attacks when he was knocked down by the blast yards from the finish line told how his legs 'just started going like noodles' and he fell to the floor.
Television viewers feared the worst when they saw footage of Bill Iffrig, 78, of Lake Stevens, Washington, crumple to the ground with the force of the first explosion in the Boston Marathon.
But as runners scattered and emergency workers ran in to help, Mr Iffrig, a retired mason, staggered to his feet and managed to cross the finishing line.
Scroll down for videos
Impact: Bill Iffrig says his legs buckled under the force of the blast, causing him to collapse to the ground
Help: Police officers with their guns drawn react as they hear the second explosion down the street while Iffrig, 78, lies dazed on the ground
Mr Iffrig became an icon of the Boston Marathon bombings after being pictured crumpled on the ground
Horrific: Mr Iffrig can be seen falling to the ground as the explosion rocked the sidelines near the finish line of the marathon
Lucky: Mr Iffrig suffered little more than a skinned knee after the blast and counts himself lucky to be alive
Mr Iffrig said he felt the impact of one of the blasts as he was feet away from crossing the finish line into what was his third Boston Marathon, and it caused him to drop to the ground.
He told Good Morning America: 'All of a sudden this enormous blast right next to me and it just kind of buckled my legs.
'So as soon as I hit the blacktop I started looking around to see how I was doing and I seemed to be OK but I didn’t get up right away.'
He told the show that a marathon worker helped him up and got him to the finish line.
He told his local paper, The Herald Of Everett, that he knew the noise was a bomb.
'The shockwaves must have hit my body and my legs just started going like noodles and I knew I was going down right there'
- Bill Iffrig, 78, who went on to finish the Boston Marathon
'It was only....feet away from me,' he said. 'It was really loud.'
He told ESPN2 he was heading for the finish line and 'feeling pretty good' when he heard a terrible explosion.
'The shockwaves must have hit my body and my legs just started going like noodles and I knew I was going down right there.'
'My legs just gave out,' he told CNN on Monday night. He said most of the runners just kept on going, but he went down because he was nearest the blast.
He said he never lost consciousness but described how he 'woke up' a little later and saw what he believed to be a part of a bomb nearby.
Mr Iffrig said what he saw was a casing that looked like a coffee can, but added: 'Then all this smoke was coming from someplace, and I wasn't able to see too much.'
A race official came to help him, and he struggled to his feet and crossed the finishing line.
78-year-old runner describes moment bomb exploded next to him
Viewers who watched the footage of the first blast will be heartened by the news of what happened to Mr Iffrig, who appeared seriously hurt as he crumpled to the ground.
While he was down, Boston Globe photographer John Tlumacki took a picture that has already become the iconic image of the explosions. It shows the elderly runner on the ground, shielding his face from the smoke as Boston police officers leap into action around him.
According to numerous reports, the bombs that detonated were packed with ball bearings. Three people died in the twin blasts and at least 183 were injured - many of them losing legs, calves or feet in the explosions.
Mr Iffrig, a veteran of 45 marathons, said he didn't even think about not crossing the finish line at the time because his head was set on the race.
Ordeal: Boston Marathon runner Bill Iffrig, pictured left with fellow runner Rebecca Roche, said he felt an 'enormous blast' and it buckled his legs
'I ended up second in my division,' he said. 'After you've run 26 miles you're not going to stop there.'
He said he finished in just over 4 hours, and suffered little more than a scraped knee.
Mr Iffrig then walked six blocks back to his hotel room, turned on the television, and realized the magnitude of what had happened.
'It was a close one though, boy. I'll tell you, that scared me,' he told his local paper.
'He's a hell of a runner. He runs a lot, and he's fast.'
- Mark Iffrig on his marathon runner father, Bill
Mr Iffrig's son, Mark Iffrig, from Seattle, was tracking his father's progress online and didn't realise what had happened until he saw news of the event and went to ring his father.
He said: 'It's horrible. He said it was quite a concussive blast. He was a little dazed. Someone helped him up - he was only about 10ft from the finish line.'
Mr Iffrig junior added: 'He's a hell of a runner. He runs a lot, and he's fast.'
The runner's granddaughter, Amanda Kilburn from Ellensburg, said she was walking across campus at Central Washington University when she heard there had been a bomb at the Boston marathon.
She said: 'I kind of freaked out and ran home to call my dad. He said my grandpa was OK.'
Bill Iffrig took up running in the 1970s to help keep him fit for his main love of mountain-climbing.
Eventually the climbing gave way to serious running, and Mr Iffrig went on to win races across the U.S.
'Impact drove me to the ground': 78-year-old describes Boston...
Boston Marathon bombings: Runner's point of view
Moment of explosion caught on camera at Boston Marathon
A race volunteer helped Mr Iffrig to his feet after the first blast, as a second explosion can be seen in the background. Mr Iffrig continue on and finished the marathon
Television viewers feared the worst when they saw footage of Bill Iffrig, 78, of Lake Stevens, Washington, crumple to the ground with the force of the first explosion in the Boston Marathon.
But as runners scattered and emergency workers ran in to help, Mr Iffrig, a retired mason, staggered to his feet and managed to cross the finishing line.
Scroll down for videos
Impact: Bill Iffrig says his legs buckled under the force of the blast, causing him to collapse to the ground
Help: Police officers with their guns drawn react as they hear the second explosion down the street while Iffrig, 78, lies dazed on the ground
Mr Iffrig became an icon of the Boston Marathon bombings after being pictured crumpled on the ground
Horrific: Mr Iffrig can be seen falling to the ground as the explosion rocked the sidelines near the finish line of the marathon
Lucky: Mr Iffrig suffered little more than a skinned knee after the blast and counts himself lucky to be alive
Mr Iffrig said he felt the impact of one of the blasts as he was feet away from crossing the finish line into what was his third Boston Marathon, and it caused him to drop to the ground.
He told Good Morning America: 'All of a sudden this enormous blast right next to me and it just kind of buckled my legs.
'So as soon as I hit the blacktop I started looking around to see how I was doing and I seemed to be OK but I didn’t get up right away.'
He told the show that a marathon worker helped him up and got him to the finish line.
He told his local paper, The Herald Of Everett, that he knew the noise was a bomb.
'The shockwaves must have hit my body and my legs just started going like noodles and I knew I was going down right there'
- Bill Iffrig, 78, who went on to finish the Boston Marathon
'It was only....feet away from me,' he said. 'It was really loud.'
He told ESPN2 he was heading for the finish line and 'feeling pretty good' when he heard a terrible explosion.
'The shockwaves must have hit my body and my legs just started going like noodles and I knew I was going down right there.'
'My legs just gave out,' he told CNN on Monday night. He said most of the runners just kept on going, but he went down because he was nearest the blast.
He said he never lost consciousness but described how he 'woke up' a little later and saw what he believed to be a part of a bomb nearby.
Mr Iffrig said what he saw was a casing that looked like a coffee can, but added: 'Then all this smoke was coming from someplace, and I wasn't able to see too much.'
A race official came to help him, and he struggled to his feet and crossed the finishing line.
78-year-old runner describes moment bomb exploded next to him
Viewers who watched the footage of the first blast will be heartened by the news of what happened to Mr Iffrig, who appeared seriously hurt as he crumpled to the ground.
While he was down, Boston Globe photographer John Tlumacki took a picture that has already become the iconic image of the explosions. It shows the elderly runner on the ground, shielding his face from the smoke as Boston police officers leap into action around him.
According to numerous reports, the bombs that detonated were packed with ball bearings. Three people died in the twin blasts and at least 183 were injured - many of them losing legs, calves or feet in the explosions.
Mr Iffrig, a veteran of 45 marathons, said he didn't even think about not crossing the finish line at the time because his head was set on the race.
Ordeal: Boston Marathon runner Bill Iffrig, pictured left with fellow runner Rebecca Roche, said he felt an 'enormous blast' and it buckled his legs
'I ended up second in my division,' he said. 'After you've run 26 miles you're not going to stop there.'
He said he finished in just over 4 hours, and suffered little more than a scraped knee.
Mr Iffrig then walked six blocks back to his hotel room, turned on the television, and realized the magnitude of what had happened.
'It was a close one though, boy. I'll tell you, that scared me,' he told his local paper.
'He's a hell of a runner. He runs a lot, and he's fast.'
- Mark Iffrig on his marathon runner father, Bill
Mr Iffrig's son, Mark Iffrig, from Seattle, was tracking his father's progress online and didn't realise what had happened until he saw news of the event and went to ring his father.
He said: 'It's horrible. He said it was quite a concussive blast. He was a little dazed. Someone helped him up - he was only about 10ft from the finish line.'
Mr Iffrig junior added: 'He's a hell of a runner. He runs a lot, and he's fast.'
The runner's granddaughter, Amanda Kilburn from Ellensburg, said she was walking across campus at Central Washington University when she heard there had been a bomb at the Boston marathon.
She said: 'I kind of freaked out and ran home to call my dad. He said my grandpa was OK.'
Bill Iffrig took up running in the 1970s to help keep him fit for his main love of mountain-climbing.
Eventually the climbing gave way to serious running, and Mr Iffrig went on to win races across the U.S.
'Impact drove me to the ground': 78-year-old describes Boston...
Boston Marathon bombings: Runner's point of view
Moment of explosion caught on camera at Boston Marathon
A race volunteer helped Mr Iffrig to his feet after the first blast, as a second explosion can be seen in the background. Mr Iffrig continue on and finished the marathon