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"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, the boy and his family were watching the Boston Marathon near the finish line when 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, CNN affiliate WHDH reported. As of 1 p.m. ET Tuesday, both were still hospitalized, according to WHDH.

The boy's father, William Richard, is a community leader in the Ashmont section of Dorchester, according to the Globe.

"My dear son Martin has died from injuries sustained in the attack on Boston," Richard said in a statement Tuesday. "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. We also ask for your patience and for privacy as we work to simultaneously grieve and recover. Thank you."

After early reports conflicted about whether William Richard ran the marathon, a family spokesperson told CNN Tuesday afternoon that he was a spectator.

At a loss: Comforting grieving parents

Tuesday morning, 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.

A 7 p.m. ET a candlelight vigil is scheduled at St. Ann Parish in Dorchester, about a mile from the home, church officials told CNN.

Neighbor Jane Sherman told CNN that William Richard came home Monday night about 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.

The boy "was a bright, energetic young boy who had big dreams and high hopes for his future, the school said in a statement. "We are heartbroken by this loss."

"We are also praying for his mother Denise, our school librarian and sister Jane, another Neighborhood House Charter student, who were seriously injured yesterday," the statement said.

The family represent "the very best this city has to offer," it said.

Also killed in Monday's attack was Krystle Campbell, who graduated from Medford High School in Massachusetts in 2001. There were no immediate details about the third victim killed in the bombings. Of the more than 170 people who were treated at hospitals, at least 17 were in critical condition and 41 in serious condition, according to hospital officials.

Martin made his "peace" sign in May when his school organized a "Peace Walk." Holding their homemade signs, kids walked around the city making a big statement with a simple act. In bubble letters, one of his classmates wrote, "No more violence!"

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 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 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.