For my whole life, Marathon Day has meant spring is here.

A lifelong Bostonian, I knew that on this day the Sox would play their only morning game, right here in Fenway Park, and then the best runners from all over the world would join regular men and women from across the country on the brutally glorious 26.2-mile trek into Copley Square. Thousands of people gather along the route early in the morning. Thousands more sit in the bleachers at Fenway and then pour out into the streets to catch the end of the big race.

A lifelong Bostonian, I’ve joined the crowds along that route. I’ve sat in the bleachers at Fenway on that day. I’ve even run that race – in 1997, when I learned the hard way that 17 miles is about the limit of my sanity but 26.2 miles is possible, even for a kid who grew up in Mattapan. As a five-term Boston city councilor, I sat in the stands at the finish line to watch those elite runners, and those regular folks, cross the finish line, every step a victory.

I’ve taken my sons there.

On this beautiful Monday, the whole family went to Fenway to watch a thrilling Sox victory with a walk-off run, and intended to stroll up to Copley to watch the marathon finish. Instead, the Sox invited kids to run the bases after the game, and we made it as far as Kenmore Square when every police officer turned and sprinted for Boylston Street.

It was hard to understand what was taking place, with cell phone service slammed and texts and tweets coming in sporadically and offering confusing, and often contradictory stories. But we walked back to Northeastern’s campus, where we had parked, and watched streams of ambulances speeding past in both directions. We saw families clutching runners. We saw clusters of people crying. Clearly, this was something horrific.

And it was. The first day of spring for this city, my city, will never be the same again. There are those who insist that Boston is resilient, and it is. There are those who insist that we won’t let this affect us, and I really hope they’re right. But I don’t see how this can’t leave a lot of scars on friends, on neighbors, on all of Boston.

There will be packed funerals and families left grieving inconceivable losses after a senseless, vicious attack. There has been and will be pain and physical therapy, massive bills and utterly changed lives for scores of wounded survivors. The first responders – the cops, the firefighters, the EMTs, the doctors and nurses and the selfless civilians who ran toward the trouble when others ran for safety – will bear wounds that don’t show up on X-rays. Boston will remain a great urban center, a magnet for tourists, a place to live, work, grow up, grow old, grow rich, grow wise … but everyone will be a little more hesitant, a little more fearful.

This was an attack in Boston, and Boston will bear these wounds with strength and dignity and courage and, yes, with many tears. But at the same time it was an attack on the world. The marathon is a global event – the top runners are international athletes who come here because the Boston Marathon is one of the greatest challenges in sports, and winning one of the greatest achievements. The flags of dozens of countries on the race route colorfully tell the story of the marathon’s reach. The litany of victims fills out that tale: Among the dead are a boy from Dorchester, beloved by his parents and siblings and teammates; a young woman from the near suburbs, embarking on a successful career; a Chinese graduate student, who came to Boston because of our preeminent educational opportunity. The wounded as well — runners and spectators — represent dozens of neighborhoods, cities and countries.

Most importantly, the marathon is an international event entirely without international animosities. We come not to cheer for our team and against the other guys, but for all the runners – for their skill, endurance and guts. The runners bond; it’s as much a social experience as an athletic one, and often they run not just for the joy of it but to raise money for a charity, to fight a disease or to help a loved one. Spectators pass water to whoever needs it, yell for whoever’s passing by, clap for the winners and just as loudly for the last man or woman to cross the line. Marathon Monday is the best of Boston, the best of world competition, arguably the best of humanity.

A lifelong Bostonian, I’m proud every year of the marathon. But I know that now it will be different. If nothing else, next year we’ll see record numbers wanting to run – to show that bad guys can take our blood but not our spirit, but more to raise money to help this year’s victims.

Wherever they came from, wherever they’re going, they are Bostonians too.

-John Tobin, who grew up in Mattapan and lives in West Roxbury, is vice president of city and community affairs at Northeastern.