Kathryn Ledwell's medal

The medal given to Kathryn Ledwell, after completing the 2013 Boston Marathon. Ledwell, 22, a Johns Hopkins University senior studying piano at the Peabody Institute, had completed the Boston marathon shortly before the bombs exploded that killed three bystanders and wounded more than 170 people. (Amy Davis / Baltimore Sun / April 18, 2013)

— At 2:42 p.m. on Monday — just minutes before the first bomb exploded along the marathon course — Carol Downing's son-in-law and daughters were positioned perfectly to watch her run past the blue-and-yellow finish line painted across Boylston Street.

Michael Gross took six, maybe seven or eight, steps away from his wife, Nicole, and her sister, Erika Brannock, until he found the spot where he planned to snap a picture of the moment they had waited for all day.

The three had been tracking Downing's progress on their smartphones as her feet touched the timing mats along the route. 30K. Done. Nearing the 40K mark …

Finally, the 57-year-old Monkton woman was approaching the final turns: right on Hereford Street and left on Boylston. Her years-long dream of running the Boston Marathon was almost complete.

Downing gripped her iPhone, which displayed a text from Nicole Gross: "We're at the finish line. When you finish head to left away from the bleachers. We're in front of LensCrafters behind the flags.

"Finish strong."

Eight minutes later, a bomb hidden in a backpack detonated near her daughters, shattering the glass on the shop's two large windows. Another detonated seconds later, farther back along the stream of runners, and closer to Downing.

Runners in front of Downing stopped abruptly. Those behind her continued forward, creating a crush of people and widespread confusion. Word spread that there had been an electrical problem at a nearby hotel.

Sirens quickly sounded. This was no accident.

Downing frantically texted Brannock and the Grosses. No answer.

Here in the heart of the Back Bay, anchored by historic buildings such as the Boston Public Library and Trinity Church, the finish-line revelry of the famous marathon took a sharp turn.

Many Marylanders who had trained long and hard for the 26.2-mile race, or had come to cheer on a loved one, would be caught up in the devastation — some injured severely, others robbed of a sense of accomplishment.

So much strength had brought them here. So much horror would send them away.

A beautiful day

Richard Snyder and his wife, Jill, Annapolis residents who married in October, had been here before. She had run the race 21 years ago; he had run it two years ago and in the 1980s, while in high school. This time, they vowed to cross the line together.

They trained together as well, with the Annapolis Striders running club, mostly along the relatively flat Baltimore & Annapolis trail. And they struck a deal: Richard Snyder would slow down a bit; his wife would kick it up a notch.

By Monday morning, they were in high spirits. The weather — mid-50s, slight breeze, a strengthening sun — seemed like a dream. "It was a beautiful day. It was perfect," says Richard Snyder, 50.

After her last Boston marathon, Jill Snyder, 52, had vowed never to run one again. But life had changed, and she had pushed herself physically to be in Boston once again, which she thought of as the "mecca" of all races. The marathon, which was marking its 117th year, is known for its qualification standards and history, as well as landmarks such as Heartbreak Hill.

"I just wanted to achieve that goal again after 20 years," she says.

As they waited at the start of the race, in the town of Hopkinton, west of Boston, they were ready. Nervous, but ready.