BOSTON — Third-grader Martin Richard had just gotten ice cream and was near the Boston Marathon finish line, eagerly watching for friends to run by. Krystle Campbell was enjoying the race with her best friend, hoping to get a photo of the other woman’s boyfriend after he conquered the last mile.

Then the unthinkable struck. The spirited 8-year-old, pictured on Facebook in his classroom holding a sign that read “No more hurting people,” was dead, along with the outgoing 29-year-old woman and a graduate student from China — victims of twin bombs that turned a scene of celebration into chaos.

More than 170 others suffered injuries that included severed limbs, shrapnel wounds, broken bones and head trauma.

While mourning the dead Tuesday, friends and neighbors tried to focus on positive memories of cherished ones whose deaths still seemed unreal to them.

Martin’s father, Bill Richard, released a statement thanking friends, family and strangers for their support following his son’s death.

Richard’s wife, Denise, and the couple’s 6-year-old daughter, Jane, suffered serious injuries in the blasts. Their older son, Henry, wasn’t hurt. Two neighbors said Jane lost one of her legs in the attack.

“My dear son, Martin, has died from injuries sustained in the attack on Boston,” Richard said. “My wife and daughter are both recovering from serious injuries. We thank our family and friends, those we know and those we have never met, for their thoughts and prayers. I ask that you continue to pray for my family as we remember Martin.”

In nearby Medford, William Campbell, described his daughter, Krystle, as the light of his life, “a very caring, very loving person.”

“Daddy’s little girl,” the 56-year-old said.

His wife, Patty Campbell, her voice breaking into tears, said the couple was “heartbroken at the death of our daughter.”

“She was a wonderful person. Everybody that knew her loved her. ... She had a heart of gold. She was always smiling. This doesn’t make sense,” she said.