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.

Jeff Bauman Jr., a man pictured in an Associated Press photo being rushed from the scene Monday in a wheelchair, lost both legs. Rescuers took the 27-year-old to Boston Medical Center, where doctors found extensive vascular and bone damage.

"Unfortunately my son was just in the wrong place at the wrong time," his father, Jeff Bauman, wrote in a Facebook post.

The younger Bauman, who had been at the race to cheer on his girlfriend, had further surgery because of fluid in his abdomen.

"I just can’t explain what’s wrong with people today, to do this to people," the father wrote. "I’m really starting to lose faith in our country."

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

"I just can’t get a handle on it," said Jack Cunningham, a longtime friend of little Martin and his family. "In an instant, life changes."

Cunningham recalled how, as a pint-sized preschooler, the boy had insisted on getting out of his stroller during a 5K race in South Boston. As soon as his mom let him out to run with the rest of the family, Martin took off along the rainy race course.

"He was just having a ball, splashing in every puddle," Cunningham said.

The boy’s father, Bill Richard, released a statement thanking friends, family and strangers for their support.

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."

U.S. Rep. Stephen Lynch, a family friend, said Martin and his family were trying to get over the race barriers and into the street after the first blast, when the second bomb struck.

"They were looking in the crowd as the runners were coming to see if they could identify some of their friends when the bomb hit," said Lynch, who has known the Richards for 25 years.

Bill Richard, a runner and cycling enthusiast who did not run the race, had to have several ball bearings removed from his leg, Lynch said.

Today, a candle burned on the stoop of the family’s single-family home in the city’s Dorchester section, and the word "Peace" was written in chalk on the front walkway. A child’s bicycle helmet lay overturned near the front lawn.

At a nearby park, "Pray for Martin" was written in large block letters on the pavement. Mourners later gathered for a candlelight vigil in the neighborhood.

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 today 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.

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.

Her mother, 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. You couldn’t ask for a better daughter," the mother said. "This doesn’t make sense."

Their daughter’s best friend, Karen Rand, suffered a severe leg injury in the blasts. "She’s very badly hurt. She’s all messed up," William Campbell said. "Her leg was all destroyed."

A friend and co-worker at the restaurant where Krystle Campbell was a manager described her as hardworking yet fun-loving, someone who knew how to live life to its fullest.

"We’d go out drinking and she’d work a double the next day," Sheba Parent said. "But she was still career-oriented and focused on her goals."

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Associated Press writers Bob Salsberg, Jay Lindsay and Pat Eaton-Robb in Boston, Katie Zezima in Arlington, Mass., Michelle Smith in Providence, R.I. and Michael Astor in New York contributed to this report.