(CNN) -- 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.
"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."
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."