More than 100 people gathered in Peabody Square on Saturday, April 15 to mark One Boston Day and share a moment of silence with the Richard family, whose 8-year-old son Martin lost his life during the bombing attack at the Boston Marathon four years ago.

The day of public service and unity commemorates those lost in the twin bombings on April 15, 2013 — BU student Lingzi Lu, and Medford’s Krystle Campbell were also killed in the blasts. MIT Police Officer Sean Collier, who was killed three days later by the bombers, and Boston Police Officer Dennis Simmonds, who died a year after he sustained injuries during a confrontation with the killers, were also remembered at the ceremony.

Standing beside a white wreath, and flanked by his wife Denise and their children, Henry and Jane, Bill Richard said, “People look at us and ask how we do it. It’s within our family, it’s the strength of our family. But if you look to your left and look to your right and look around, this is the reason,” he said. “This is how we do it. This is how we get by. This is how we move forward.

He added: “And One Boston Day, while it’s about hanging wreaths and reflecting, it’s about moving forward for us as a family and as a community.”

Mayor Martin Walsh and Gov. Charlie Baker joined in the moment of silence at 2:49 p.m. — the time of the first explosion — as the bells of All Saints’ Church rang out. “It’s just amazing that the community that we’re in today, Dorchester, it’s just amazing that every time you’re asked, you rise to the occasion,” Walsh said.

Earlier that afternoon, volunteers cleaned and beautified stretches of Dorchester Avenue. New plantings stood in the square. Food tents and canvasses bearing messages of solidarity rose outside Ashmont Station. Members of Team MR8, some of whom would run the Marathon two days later, draped blue and white ribbons around the Peabody Square clock tower.

“The work you did today, it looks incredible,” Bill Richard said. “I just want to thank you on behalf of our family, and you know, when we go across the street for hot dogs and ice cream and some drinks today, think of Martin, ‘cause I mean like most kids, it was his favorite food.”

A number of runners from Dorchester plugged along and made it through the Boston Marathon’s 26 miles and 385 yards of winding road from Hopkinton to Boylston Street.

As temperatures hit the mid-70s on an unseasonably warm Monday holiday on April 17. The 100-member Team MR8 raised $917,431 for the Martin Richard Foundation.