WASHINGTON — On April 15, Cynthia Smith and her husband grabbed some post-lunch coffee and headed to a spot in front of the Lord and Taylor department store to watch the runners cross the finish line in the Boston Marathon.

The Red Sox game at nearby Fenway Park was in the late innings. Along curbsides, spectators were urging on the leaders in the famed 26-mile race.

“It was a beautiful day, I was updating my Facebook page all day saying, you know, ‘having a great time,’” Cynthia recalls.

They were listening to supporters cheer the runners as they mustered their strength for the finish — and looking at struggle on competitors faces, recalling how they felt at that point when they ran the Disney World Marathon in 2012 — their first.

They were laughing when they heard the first explosion. It took a few seconds for the ripple of fear to reach where they were standing, and that’s when Cynthia and Murdock Smith, 32, knew something bad was happening. Then a second blast took place, right across the street from them.1

“We didn’t know if the buildings were coming down, you just have no sense of what’s going on,” the 29-year-old Cynthia said.

The couple, who started running five years ago, went to watch the Boston Marathon to “absorb people’s motivations,” so they could train and run their second marathon — the Marine Corps Marathon. This Sunday, despite their experiences, despite being just feet away from the blast in Boston on April 15, despite the persistent fear in the weeks that followed, they will run. They are still running because unlike others, they still can, Cynthia said.

“You just can’t stop and stand still because I did that the first few days, I just stopped,” Cynthia said. “… You have to go on, you have to keep moving forward.”

“It is just gut wrenching to know that so many people lost so much that day,” she said.

The Marine Corps Marathon on Sunday is one of the largest marathons in the U.S., with more than 30,000 registered runners. Organizers said making event security is a top priority.

Six-hundred Marines, 300 sailors and 600 emergency services personnel will be on hand to maintain safety, said Col. David Maxwell, commander of the Marine Corps Base in Quantico, Va.

“As you run past those monuments that are reflections of our history and our liberty and our freedom, those service members are out there cheering you on,” Maxwell said at a press briefing Friday.

Marathon organizers said they are working closely with threat analysis agencies, seven law enforcement agencies and first-response teams. They say they have incorporated lessons the Boston police chief learned from the attack there, in which three people were killed and over 200 were injured.

Like the characters at the Disney World Marathon, the Marine Corps Marathon has mascots of its own, Maxwell said.

“The Disney marathon has Mickey and Minnie, the London marathon has Big Ben, the Marine Corps Marathon has the U.S. Marines,” he said.

Cynthia is glad the Marines’ will be there to step in, to assist people if anything were to go wrong. But even more, the Marines’ symbolize the patriotic spirit, she said.

“It’s just amazing for them to come out and support average runners like us and be there to cheer us on,” she said.

Oh yes, and the Boston Red Sox? They’re still competing, too — in the World Series.