Story highlights Witnesses at the scene of the Boston bombings recall the horror

A Boston.com producer was at the finish line and captured the first bomb with camera

One woman describes seeing people "literally flying through the air"

Another says she couldn't get the chill to go away

Linda Claire Willits crossed the finish line at the Boston Marathon in a time of 3 hours and 34 minutes, setting a personal best in her 29th marathon.

No matter how many races one runs, there's nothing like that euphoric moment of pushing through the pain to complete 26.2 miles. Willits soaked in the atmosphere along Boylston Street. People lining the road cleared a path when they saw she was a runner. They congratulated her and made her feel like a celebrity.

She texted a friend waiting down the street at the bar at the Mandarin Oriental hotel. "I'm on my way," Willits said.

Her friend, Stephanie Douglas, prepared to celebrate.

Then, a small explosion went off, followed seconds later by a thunderous boom that tore through the area.

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Photos: Deadly attack at Boston Marathon Photos: Deadly attack at Boston Marathon An injured man is loaded into an ambulance after two bombs went off near the finish line of the Boston Marathon on April 15, 2013. Three people were killed and at least 264 were injured. Hide Caption 1 of 55 Photos: Deadly attack at Boston Marathon A man comforts a victim on the sidewalk at the scene of the first explosion. Hide Caption 2 of 55 Photos: Deadly attack at Boston Marathon The second explosion goes off near the finish line. Hide Caption 3 of 55 Photos: Deadly attack at Boston Marathon The first explosion knocked down 78-year-old runner Bill Iffrig at the finish line. He got up a few minutes later and finished the race. Hide Caption 4 of 55 Photos: Deadly attack at Boston Marathon A runner embraces another woman on the marathon route near Kenmore Square. Hide Caption 5 of 55 Photos: Deadly attack at Boston Marathon Former New England Patriots offensive lineman Joe Andruzzi carries a woman from the scene. Hide Caption 6 of 55 Photos: Deadly attack at Boston Marathon A victim of the first explosion is helped on the sidewalk of Boylston Street. Hide Caption 7 of 55 Photos: Deadly attack at Boston Marathon An injured person is taken away from the scene in a wheelchair. Hide Caption 8 of 55 Photos: Deadly attack at Boston Marathon A woman kneels and prays at near the finish line. Hide Caption 9 of 55 Photos: Deadly attack at Boston Marathon People run down Exeter Street after the blasts. Hide Caption 10 of 55 Photos: Deadly attack at Boston Marathon The explosions occurred around 2:45 p.m., about an hour after the first of the race's nearly 27,000 runners had crossed the finish line. Hide Caption 11 of 55 Photos: Deadly attack at Boston Marathon Victims lie on the ground at the scene of the first explosion. Hide Caption 12 of 55 Photos: Deadly attack at Boston Marathon A couple runs from the scene pushing a stroller. Hide Caption 13 of 55 Photos: Deadly attack at Boston Marathon A runner reacts near Kenmore Square after the explosions. Hide Caption 14 of 55 Photos: Deadly attack at Boston Marathon A man's blood-stained feet hang outside an ambulance. Hide Caption 15 of 55 Photos: Deadly attack at Boston Marathon A bystander who was injured in the first explosion is wheeled across the finish line while receiving medical attention from rescue workers. Hide Caption 16 of 55 Photos: Deadly attack at Boston Marathon Carlos Arredondo was at the race handing out American flags to spectators. After the blasts, he helped emergency responders and is credited with helping a man survive serious leg wounds. Hide Caption 17 of 55 Photos: Deadly attack at Boston Marathon The second explosion goes off near the finish line. Hide Caption 18 of 55 Photos: Deadly attack at Boston Marathon Police look at blown-out windows. The bombs shook buildings, witnesses said, sending people to seek shelter under tables. Hide Caption 19 of 55 Photos: Deadly attack at Boston Marathon Unclaimed runners' bags fill an area near the marathon finish. Hide Caption 20 of 55 Photos: Deadly attack at Boston Marathon Women desperate to hear from loved ones are unable to get close to the site of the attack. Hide Caption 21 of 55 Photos: Deadly attack at Boston Marathon Police and runners stand near Kenmore Square after the attack. Hide Caption 22 of 55 Photos: Deadly attack at Boston Marathon Runners gather near Kenmore Square after the explosions. Hide Caption 23 of 55 Photos: Deadly attack at Boston Marathon An EMT worker is transferred to an ambulance outside a medical tent in Copley Square. Hide Caption 24 of 55 Photos: Deadly attack at Boston Marathon A SWAT team arrives on the scene. Hide Caption 25 of 55 Photos: Deadly attack at Boston Marathon A runner sits near Kenmore Square after the attack. Hide Caption 26 of 55 Photos: Deadly attack at Boston Marathon Runners who had not yet finished the race are stopped after the explosions. Hide Caption 27 of 55 Photos: Deadly attack at Boston Marathon Victims are helped at the scene of the first explosion. Hide Caption 28 of 55 Photos: Deadly attack at Boston Marathon A man in tears is helped at the scene on Boylston Street. Hide Caption 29 of 55 Photos: Deadly attack at Boston Marathon Passersby put pressure on a victim's leg to try to stop the bleeding. Hide Caption 30 of 55 Photos: Deadly attack at Boston Marathon Massachusetts State Police guard an area near Kenmore Square. Hide Caption 31 of 55 Photos: Deadly attack at Boston Marathon Bystanders embrace near the finish line. Hide Caption 32 of 55 Photos: Deadly attack at Boston Marathon Police officers gather on Newbury Street. Hide Caption 33 of 55 Photos: Deadly attack at Boston Marathon Women and children are escorted away from the scene. Hide Caption 34 of 55 Photos: Deadly attack at Boston Marathon Bomb squad officials check a possible suspicious device near the scene of the blasts. Hide Caption 35 of 55 Photos: Deadly attack at Boston Marathon A woman is comforted after the blasts. Hide Caption 36 of 55 Photos: Deadly attack at Boston Marathon Two injured women are taken away on stretchers. Hide Caption 37 of 55 Photos: Deadly attack at Boston Marathon An injured woman is loaded into an ambulance. Hide Caption 38 of 55 Photos: Deadly attack at Boston Marathon First responders load injured people into an ambulance. Hide Caption 39 of 55 Photos: Deadly attack at Boston Marathon An injured man is prepared to be moved from a stretcher to an ambulance. Hide Caption 40 of 55 Photos: Deadly attack at Boston Marathon An injured woman is placed on a stretcher. Hide Caption 41 of 55 Photos: Deadly attack at Boston Marathon A runner is comforted following the attack. Hide Caption 42 of 55 Photos: Deadly attack at Boston Marathon The Cambridge Police Department's bomb squad investigates unattended personal items left behind after the explosions. Hide Caption 43 of 55 Photos: Deadly attack at Boston Marathon Bystanders check their mobile devices for news of the explosions. Hide Caption 44 of 55 Photos: Deadly attack at Boston Marathon A member of the bomb squad investigates a suspicious item on the road near Kenmore Square. Hide Caption 45 of 55 Photos: Deadly attack at Boston Marathon A runner in a wheelchair is taken from a triage tent after the explosions went off. Hide Caption 46 of 55 Photos: Deadly attack at Boston Marathon People comfort each near the site of the blasts. Hide Caption 47 of 55 Photos: Deadly attack at Boston Marathon Racers and race officials stand by after the explosions. Hide Caption 48 of 55 Photos: Deadly attack at Boston Marathon Emergency personnel respond to the scene. Hide Caption 49 of 55 Photos: Deadly attack at Boston Marathon Police and emergency crews tend to victims. Hide Caption 50 of 55 Photos: Deadly attack at Boston Marathon An injured woman is carried away on a stretcher. Hide Caption 51 of 55 Photos: Deadly attack at Boston Marathon A man lies on the ground after the incident. Hide Caption 52 of 55 Photos: Deadly attack at Boston Marathon Officials watch as the first explosion goes off on Boylston Street. Hide Caption 53 of 55 Photos: Deadly attack at Boston Marathon Spectators leave the bleachers after the explosions. Hide Caption 54 of 55 Photos: Deadly attack at Boston Marathon Police inspect one of the blast sites. Hide Caption 55 of 55

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"It was so strong the bar filled up with smoke and chairs tipped over," Douglas said. "I saw people -- it was like they were on a trampoline literally flying through the air."

Bedlam ensued. Smoke poured into the bar. People began shouting that another bomb had been found, and everyone scrambled to escape.

Outside, one man's legs were blown off, and he kept trying to stand up.

Douglas fled, unable to contact Willits. Panic for her friend sunk in.

Rushing to the scene

Boston.com sports producer Steve Silva was covering the much-heralded Boston Marathon. He was shooting what should have been joyous finish-line scenes when in a few seconds, everything changed. His camera kept rolling amid screams of shock and horror.

"It was just immediately (evident) there were injuries, right in the middle of the spectator crowds. I saw dismemberment, I saw blood everywhere," Silva said.

"I saw someone lose their leg, people are crying, people are confused."

Rescuers rushed to the victims with stretchers and wheelchairs. Ambulances quickly lined up for blocks and blocks. In between the screams of pain and panic were phone calls. "Mom, I'm safe."

They were words Boston Globe reporter Billy Baker heard many times as he kept passing people on the scene. He posted what he heard and saw on Twitter: "Finish line volunteers told to run. Describe fear 'like 9/11 or the tsunami.'"

He described a nervous calm energy as people either tried to figure out what was happening or had no idea where to go.

Then his tweets got considerably more grim:

"Now getting gruesome first-hand accounts of hair on fire, severed limbs, battlefield scene in front of Charlesmark Hotel."

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Confusion. Bewilderment. Rumors everywhere.

"It's not safe to be here," said a Boston police officer evacuating Commonwealth Avenue, Baker reported.

Jim Bardin works in an office building between the locations of the two blasts.

"I heard the first blast and it shook the building a bit, and went to see what was going on and the second one went off a couple of seconds after," Bardin said.

What he saw from above was harrowing.

"People were pretty panicked down there -- the crowd was trying to get away as fast as possible. From up above, it looked like mayhem."

Will Ritter was about a block away, near Copley Square. He was trying to arrange a press conference for a runner who had just finished the race.

He said the blasts felt and sounded like the concussion bursts at the end of a Fourth of July fireworks show. Then he saw the white smoke billowing. Then emergency vehicles -- and pandemonium.

"Let's go, Let's go," shouted rescue workers.

Mark Gordon had just moved to his high-rise apartment on Boylston Street a month and a half ago. He had a perfect view of the marathon from his balcony and throughout the day, he had looked out and snapped photos.

It was a glorious day in Boston, the city he'd lived in for 12 years.

He was doing household chores when the first bomb went off. "I'll never look out my window the same way again even though it's been six short weeks," Gordon said.

Brittany Smith, a physical therapy student at Northeastern University in Boston, was volunteering at Medical Tent B, two blocks away from the finish line. She was treating runners for common ailments like muscle cramps when she heard the first loud bang.

"Everyone's like, 'What's going on?' You could just sense something was wrong, that things were definitely not right," Smith said.

"We didn't rush to the scene, I was trying to (help) a marathoner locate her family members ... and I'm freaking out. It was really hard to focus on helping out the marathon runner. I was just panicking," she said.

She and other volunteers were desperate for information. They turned on the news and saw the footage from helicopters whirring above.

The sidewalks had turned crimson.

Running for a cause

Willits was en route to meet her friend at the Mandarin Hotel when excitement from finishing the race turned into terror. "The whole ground shook, and I knew right away it was a bomb," she said.

Crying, she added, "I saw people who had lost their limbs."

Douglas worried about the fate of her friend. They could not reach each other by cell phone.

Douglas had come up from Virginia to cheer on her friend. She couldn't help but think of 2008 when she was in Mumbai when deadly shooting and bombing attacks broke out there. "This is twice I've been in two cities when this kind of thing has been happening," she said.

Douglas knew Willits was somewhere in the vicinity when the blasts went off. After all, she'd gotten the text from her. "Everything that could go wrong was gong through my head," she said.

Minutes seemed like hours. Finally, Willits' daughter managed to get hold of both of them by phone and coordinated their reunion. Willits waited at a street corner for nearly an hour.

"We were both already crying and just embraced each other," she said.

Added Douglas, "It was a meltdown."

About that time, another blast went off and they trembled again. They would later learn it was a controlled explosion by police. Strangers offered them shelter and gave them water.

"I'm kinda numb right now," Willits said. "Having seen what I saw, it really breaks my heart."

She had begun running marathons a decade ago for her daughter after she was diagnosed with rheumatoid arthritis. She and Douglas had pledged Sunday to run the Twin Cities Marathon together later this year.

They were even more determined now.

"This has been a traumatic event," Willits said between tears. "But I just feel like we can't stop doing things that we enjoy doing, because then the terrorists win."