Next-door neighbor Betty Delorey said Martin loved to climb trees and play sports with his brother and sister and the other children in the neighborhood.
"I can just remember his mother calling him, 'Martin!' if he was doing something wrong," the 80-year-old said. "Just a vivacious little kid."
A photo of the three Richard children on Halloween in 2009 showed a smiling Martin dressed as Woody from the "Toy Story" films, complete with cowboy hat and sheriff's badge. Beside him stood Jane, dressed as the film character Jesse, and Henry, dressed as Harry Potter.
"He had that million-dollar smile and you never knew what was going to come out of him," said Judy Tuttle, a family friend. "Denise is the most spectacular mother that you've ever met and Bill is a pillar of the community. It doesn't get any better than these people."
She recalled having tea recently with Denise Richard, a librarian at the children's elementary school, while Martin did his homework.
"What a gift," Tuttle said of Martin. "To know him was to love him."
Kevin Andrews, headmaster at the Neighborhood House Charter School, said the school community was heartbroken by the loss of the third-grader, whom he called "a bright, energetic young boy who had big dreams and high hopes for his future."
Cardinal Sean O'Malley, head of the Roman Catholic Church in Boston, said a Mass on Tuesday in Israel for victims of the bombing, archdiocese officials said. He also called the pastor of St. Ann parish in Dorchester, where the Richards attend church, to say he was praying for them.
Boston University said one of the victims was a graduate student who was watching the race with friends at the finish line, which is not far from the school. The Chinese Consulate in New York said the victim was a Chinese national, though it did not identify the student. A Hong Kong broadcaster reported the student was a woman from Shenyang studying statistics. The official Chinese news agency Xinhua reported her relatives have requested she not be identified.