A banner at Rowes Wharf on the first anniversary of the Boston Marathon bombings
It started as a celebratory scene in Boston's Copley Square on April 15, 2013, as thousands gathered to cheer on runners crossing the finish line at the Boston Marathon, a proud New England tradition for 117 years.
Yet in a flash the site transformed from one of triumph to one of tragedy as a bomb suddenly exploded, and then another, in a terrorist attack
that killed three and injured nearly 300.
Today, on the first anniversary of the Boston Marathon bombing
, people took to Twitter, Instagram and other social-media sites to remember those lost and to honor the "Boston Strong" spirit that emerged in the city.