(CNN) -- Almost a year ago, 8-year-old Martin Richard wrote four simple words on a sign at school.
"No more hurting people," it said. For the camera, he held up the bright blue sign decorated with hearts framing the word, "Peace."
It's a photograph that many find difficult to look at Tuesday as they struggle to comprehend the violence that took Martin's life. On Monday, he was watching the Boston Marathon, excited to see his dad cross the finish, CNN affiliate WHDH said. Two bombs exploded just off Copley Square in the heart of the city.
The grade-schooler was killed, authorities said.
Martin's mother, Denise, and his sister were grievously injured, The Boston Globe reported.
Denise Richard underwent surgery for an injury to her brain and Martin's 6-year-old sister lost her leg, WHDH says. As of 1 p.m. ET Tuesday, both were still hospitalized, the TV station reported.
The boy's father, Bill Richard, is a community leader in the Ashmont section of Dorchester, according to the paper.
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Early Tuesday, people arrived at the Richards' home in the working-class neighborhood dotted with large New England-style homes. On the stone steps of the Richards' blue-gray house, visitors gingerly laid down flowers. Someone had written "peace" at the end of the driveway, according to the Globe.
Neighbor Jane Sherman told CNN that Bill Richard came home last night around 10:30. He seemed extremely upset and didn't appear to want to talk, she said.
On Tuesday at the Richard home, a 10-year-old girl who went to school with Martin came by with her mother.
"We came here to pay our respects," the mother told CNN. "My daughter was very sad. He was a very nice boy."
Martin attended the Neighborhood House Charter School, according to a school official.
Martin made his "peace" sign last May when his school organized a "Peace Walk." Holding their homemade signs up, kids walked around the city making a big statement with a simple act. In bubble letters, one of his classmates wrote: "No more violence!"
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In another photo of Martin -- this one apparently marking what was perhaps his first Communion -- he is smiling, missing a few teeth, handsome and proud in his white suit. He holds a colorful Communion banner. On it is a dove that symbolizes the Holy Spirit.
The Richard family was apparently very active in the neighborhood.
"They are beloved by this community," City Councilor at Large Ayanna Pressley told the Globe. Pressley and other devastated residents gathered at Tavolo Restaurant in Dorchester to mourn.
The family contributes "in many ways," she said. "That's why you see this outpouring. It's surreal, it's tragic."
Sherman said that the Richard family is a "typical all-American family" and that the Martin and his little brother always loved to play in their yard, no matter the weather.
Neighbor Dan Aguilar told the Boston Globe the same, and said he was having a hard time wrapping his mind around the child's death.
"That little boy will never come home again,'' he told the paper. "It's still unreal. I have no words. I have no words.''
While so much grieving continues, more details are emerging about Monday's bombings.
No suspects have been identified in the case, which federal authorities are classifying as an act of terrorism. It was not immediately known whether the origin of the bombings was domestic or foreign.
The intelligence community is poring through all threat reporting for any clues, U.S. counterterrorism officials told CNN. That includes any claims made on jihadist websites.
Nothing is being dismissed this early on, the officials said.
CNN's Gary Tuchman contributed to this report.