But a shocked running community is resolving to flock to Boston next year, despite mounting fears that officials may move to restrict Boston Marathon entries even more because of the deadly bombings.
- CBC's John Rieti speaks to Canadians after the Boston Marathon bombings
- How the Boston Marathon bombings unfolded
Rob Thomas started running four years ago, just before the birth of his first son. Three children and one Boston Marathon experience later, in 2010, Thomas is still pounding the pavement and now wants to return to race in Boston "more than ever."
Return to 'the temple of running' pledged
Even his wife, a supportive non-runner, told him he must aim to return to Boston, a place he calls "the temple of running."
He thinks fellow runners will have the same reaction and that should make the race even more popular following Monday's bombings, which are now the focus of a worldwide investigation by the FBI.
That's not to say the race was struggling in popularity before. It draws more than 20,000 entrants, who must qualify by running one of several approved marathons in a time set for their age and gender. It also draws about 500,000 spectators annually.
In 2010, when Thomas ran, prospective runners filled up all available spots for the marathon in a record-setting eight hours and three minutes. So officials decided to tighten the qualifying times for all age divisions and prioritize the faster runners in future years.
Thomas said he's worried officials may restrict runners even more after the this week's bombings.
If the reaction is to scale back, "I feel badly for the people who really, really want to run it now and have that extra motivation" because of what just occurred, he says.
Increased security expected
Jennifer Faraone is one of those marathon newbies with renewed motivation. She is a running coach whose recurring injuries have limited her to half-marathons and delayed her plans to run the Boston Marathon for almost a decade.
She's increasingly determined to qualify for a spot now, and hopes the bombings don't result in officials lowering the number of people allowed to race next year.
"I think this is where the running community needs to stick together and still go to these events," she said, adding how important it is to show strength in the face of adversity.
Still, she expects the 2014 Boston Marathon will have additional security measures that will make attending harder and more inconvenient.
"I'm concerned about what it's going to mean for all the races to come," she said.
While upcoming marathons, such as the one scheduled for next Sunday in London, U.K., and for early May in Vancouver, B.C., and Toronto, Ont., are blazing ahead, official conversations around heightened security have already started.
Ontario hosts two marathons May 5, and the Mississauga and Toronto marathon race directors have already scheduled meetings with local police to discuss increased security measures.
Meanwhile, British officials for this weekend's London marathon, which hosts about 37,000 runners and draws half a million fans, are taking a second look at security arrangements.
Lawrence Hill, a Canadian author, echoed some of these concerns about increased marathon safety in an interview Tuesday with CBC's Jian Ghomeshi.
Hill was there to discuss his new book, but the life-long runner wanted to speak to the "incredibly hateful and devious attack on something so sacred."
He expects runners will now have to check their bags at future races rather than throwing them down on the sidewalk, like he's grown accustomed to doing at races.
"It seems like the end of a certain innocence," he said.
A runner's holy grail
"I'm just shocked," said Sean Squires, who completed the 2012 Boston Marathon and attended this year's event to cheer on teammates from his training group, the Beaches Running Club. At his hotel after the race, he watched runners come back, draped in recovery blankets, crying and in shock.
Squires is already qualified for next year's Boston race thanks to a speedy Hamilton, Ont., run last November. He guessed about eight of his 12 teammates who ran Sunday met their target qualifying times for next year as well.
His gut feeling? Not only will he and those who have qualified go back, but also that all the Beaches Running Club members who haven't yet secured a spot will train harder to have the chance to attend the 2014 race.
"It would be terrible if something like this would kill an event like that," he said.
He says there are lots of reasons why the Boston Marathon is the holy grail for running fanatics, including its tough qualifying times and long history. But he also notes that it is the atmosphere in Boston that makes the experience.
"All along that route people are out supporting you, cheering you on for pretty much the whole 26 miles," says Squires. "It's just an unbelievable feeling."
In fact, Boston Marathon hopeful Dan Quai, who missed his age division's qualifying time in his last marathon but plans to try again, says Monday's tragedy may spur more public support for the event and that even larger numbers of supporters may line next year's route.
"I think it will bring out more people to support people who were put in harm's way."