MARTINEZ -- Katherine Hern could feel the exhilaration building as she strode closer to the Boston Marathon finish line. Her family was waiting in Boston to celebrate her achievement.

A race-provided text message for the families of race entrants let Katherine's family -- husband Alan, daughter Abby and son Aaron -- know that she was about a minute away from their perch on Boylston Street. So Alan Hern moved from his spot, and Aaron also adjusted where he was watching.

Then, what should have been a moment of celebration became one of confusion and terror.

"I was running and the first explosion went off," Katherine said Friday. "It didn't really sink in what happened and we all kind of kept going. Then the second one went off, and I knew something big was going on."

Within seconds, she said, her adrenaline turned to fear. Her family was in the area of the blasts.

Aaron, it turned out, was just feet away from the second bomb and closer still to Martin Richard, the Massachusetts 8-year-old killed in the explosion.

She had a cell phone, but security was already holding people back from the scene.

Somewhere close by, Alan Hern was escorting Abby to a nearby restaurant to leave her with family friends. When he got there, he said, he realized Aaron wasn't with him.

He raced back and saw Aaron bleeding, his bone exposed from shrapnel wounds.

"I didn't see anything major near his torso, which made me feel better about his chances to survive," Alan Hern said.

The family told NBC's Today Show that a passer-by made a tourniquet out of a belt to slow the bleeding. Aaron, silent and calm, was taken to Children's Hospital in Boston.

Two surgeries later, he's been cleared for almost all activities, with swimming the lone exception. Aaron suffered damage to his eardrum and won't be cleared to return to the pool for several weeks.

"It's really amazing to see how he's come from breathing tubes and IV's to where he is now," Alan Hern said Friday, a day after his son had 86 post-surgery staples removed from his left leg. "Now he's just trying to regain the strength he's lost and his mobility."

That he's able to breathe at all, much less walk, still strikes the Herns as overwhelming.

"The miraculous thing is, we had just left our spot where we were," Alan Hern said. "We were right where the first bomb was believed to go off. People behind us were hurt. People around us were hurt."

The whole experience has, in the words of Alan Hern, "changed our world."

Initially angry over the bombings and the pursuit of the bombing suspects in the days that followed, Alan Hern said that emotion soon evaporated with his son's improvement. It was replaced, he said, by sheer incredulity.

"It makes you wonder what goes on in someone's mind," Alan Hern said. "It brings a new perspective. You hear about the issues in the world ... and you see what it looks like as a human, instead of just on television."

Katherine Hern said she will take with her not all bad memories of the family's trip to Boston, but she stopped short when asked if she'd go back and do it again.

"I'm not sure I could ask my family to go through that again," she said. "We'll see."