Mark Begor had just crossed the finish line at the Boston Marathon Monday when literally moments later his wife Kristen heard an explosion, felt the concussion and knew something was terribly wrong.

Cory Lee had already finished running and was in the medical tent, receiving intravenous fluids for dehydration. She heard the explosion, too, and the look on the faces of the people around her told the story.

The noise was a bomb exploding at around 2:50 p.m., amid spectators on Boylston Street near Copley Square. Seconds later another bomb went off several hundred feet away. As of Wednesday, three people had died and more than 170 were injured.

“I heard it loud and clear, but to be honest I’m still hearing it,” Ms. Lee told The Bulletin on Tuesday. “I lived in the city for so long and was immune to loud sounds. This was unlike any sound I ever heard.” Upon leaving the medical tent she saw people running everywhere. “It was very apocalyptic.”

Ms. Begor had gone to Boston to accompany her husband, Mark, who was running in his second Boston Marathon.

Mr. Begor was not feeling well on Monday. Suffering from a cold and congestion, he was running for the Marathon Strides Against MS team of the National Multiple Sclerosis Society, so he did not give in to his discomfort.

“He wasn’t running his best because his legs cramped up at mile 16 and he was just trying to make it through,” Ms. Begor said. “I saw him at the 17th mile and he said, ‘I’m dying.’” Ms. Begor urged him on.

Mr. Begor, a seasoned marathon runner who has also run three times in New York City, and once each in Hartford and Washington, D.C., normally finishes in three and a half hours, but Monday he was behind his usual pace.

As it turned out, he came in at 4:03. The first bomb went off at 4:09.

“After I saw him pass through, I said, ‘This is good, we’re done,’” Ms. Begor said. She was standing with two friends from Boston, and after Mr. Begor finished, she said to them, “‘Let’s go,’ and we walked 15 to 20 feet” and then she felt the blast. They had been standing in front of the building where the bomb went off.

“I had no idea what that noise was,” she said “I thought, That’s odd. I looked back and saw smoke and rubble. I grabbed both my friends’ hands and started moving, and then there was a second blast and I thought, This is a real problem.” She was afraid there might be a third.

They were on a narrow section of sidewalk behind the bleachers holding spectators when the blasts went off.

“After the second blast people started to panic,” she said. “My friend saw an older woman with a walker go down.”

Still holding hands, the three made a left on Dartmouth and then made their way to their friends’ condo on Commonwealth Avenue.

“Everybody was just panicking,” she said. “We got back to the condo and sat on the steps. People kept asking us what happened. A young man came up to us and said, ‘Can I use your phone to call my mother?’”

The city cut off cell service, but Ms. Begor was still able to text, and so she texted Mr. Begor, their children and other family members. Like Ms. Lee, Mr. Begor had to retrieve his cell phone and he finally was able to reply.

“He eventually called and was sort of in tears. It was just very scary,” Ms. Begor said.

For the full story, see Thursday’s Wilton Bulletin.