Jill Beccaris-Pescatore of Glenside had just finished the Boston Marathon and was about a block and a half from the finish line when she heard two explosions.

"It sounded bomb-like," said Beccaris-Pescatore, 45, a veteran marathon runner. "It was something that didn't sound right, and everyone was concerned."

Runners and spectators from the Philadelphia area described a gorgeous day - "perfect running weather," said Beccaris-Pescatore - that turned into a nightmare.

Emily Russo, 20, a Haddonfield High School graduate, had just cheered as her Tufts University schoolmates passed the 26-mile mark. She turned her back to leave when the ground shook.

"I always think the worst, so I was freaking out," she said.

"I thought it was a bomb."

Russo turned around to face the race, and people were standing frozen, confused.

Seconds later, there was another explosion.

"The crowd started to scream and run," she said.

Russo and her friends joined hands and ran. She looked back and saw smoke billowing over a high-rise building.

"I started to cry," she said. "That's when it really hit me. That freaked me out. I just saw my two friends run by. I was scared, thinking the worst - that they'd gotten hurt."

A woman nearby was hunched over, sobbing uncontrollably. Russo said she had never seen someone cry that hard.

Greg Bielecki, 32, a running coach at La Salle College High School, had finished the race and returned to his mother-in-law's house in the Boston area when he learned about the twin blasts. One occurred right where his wife and mother-in-law had stood for the entire race while he ran.

"They were standing in the exact spot of the explosion," he said, describing the finish line in front of the Marathon Store on Boylston Street.

Brad Spicer, a 37-year-old teacher from Salem, N.J., finished the marathon in 3:02 - about an hour before the blast.

He said his mother, father, 6-year-old son, and 11-year-old nephew spent four hours at the site of the first bomb but left because he finished the race.

"They were right there," Spicer said. "They were standing right there for four hours. My son and nephew went into that candy store. They were right there in front of that sporting-goods store where the bomb went off."

Jon Strauss, 37, was a few blocks away, walking home from a Red Sox game, when the chaos erupted. "You could see a plume of smoke rising up, and people were running away," said Strauss, a Lehigh University graduate who lives in North Andover, Mass.

Strauss said groups of people were fleeing nearby Copley Square while others, who did not know what had happened, were walking toward the finish line to see runners complete the marathon.

"There was nothing but the sound of sirens and emergency vehicles everywhere," he said. "It was deafening."

He added: "There were people openly weeping. There were people freaking out because they couldn't get in touch with people. There are a lot of people there to meet with runners after the race, and they didn't know where to go."

Paige Bradley, a senior at Boston University from Blackwood, Camden County, was walking with friends toward the finish line when they stopped into a restaurant and saw the explosion on TV.

"It's so awful. My friends from all over are texting me to see if I'm all right," said Bradley, who attended Bishop Eustace Prep. "I don't think security has any checkpoints - they didn't check us - but who thinks something like this would happen? I'm sure they'll change things now."

John Schwab, 45, of Haddonfield, had just finished his first Boston Marathon in 3:24. He and a group of other runners from the Moorestown running club and the South Jersey Athletic Club had agreed to rendezvous after the race in a hotel bar a block from the finish. They were in the back of the bar when the bomb went off and heard nothing. They found out when people tried to leave the bar and weren't allowed.

"It was an unbelievable turn of events," Schwab said. "Since the minute it happened, people became hysterical. It was outrageous."

For Beccaris-Pescatore, the sound of the blasts was followed by confusion.

One man next to her suggested it could have been the sound of a cannon fired for Patriots' Day, a holiday commemorating the Battles of Lexington and Concord.

"At this point we still didn't know what was going on," she said.

But something was wrong.

Looking toward the finish line on Boylston Street, she could see billowing smoke, and people running toward her.

Then police rushed in to clear the way for emergency vehicles, she said.

It was a surreal scene because she had just completed a grueling marathon: "Time stands still and you're kind of groggy," she said.

It was her 15th marathon and her first Boston, though she has attended as a spectator.

Before she left for her hotel with her husband and son, she had heard speculation at the scene about bombs in garbage cans or the sewer.

She checked Twitter on her iPhone and initially saw very little information. When she returned to her hotel and checked again, she saw that "Twitter was just blowing up."

And she finally watched the news on TV and saw confirmation of the terrible toll.

"It is so tragic and deplorable," she said. "I'm so angry about it."

Boston "is so wonderful and so accommodating" for the marathon, she said, and she vowed not to be deterred by the horrible events.

"We're going to be back next year," she said.

at 215-854-5983 or bmoran@phillynews.com, or follow @RobertMoran215 on Twitter.

Contributing to this article were Inquirer staff writers Phil Anastasia, Barbara Boyer, Sam Carchidi, T.J. Furman, Chris Palmer, Darran Simon, and Michael Vitez.