The blasts killed eight-year-old Martin Richard just after he had hugged his father.
Krystle Campbell also died. Her family was mistakenly told she was only wounded. Her father was taken to a hospital bed, expecting to see his injured daughter. Instead, it was another woman, who had been badly hurt in the Boston Marathon bombings.
The third of the three people killed in Monday's blasts was a Boston University graduate student who was watching the race with two friends, the university said on Tuesday.
The Chinese graduate student at Boston University was originally from China's northeastern city of Shenyang, a state-run Chinese newspaper reported Wednesday. The Shenyang Evening News said on its official Twitter-like microblog account that the victim's name is Lu Lingzi. An editor at the newspaper said that Ms. Lu's father confirmed his daughter's death when reporters visited the family home. The editor declined to give his name because he was not authorized to speak to foreign media.
The Chinese Foreign Ministry and Consulate General in New York are not releasing the victim's name at the request of the family. But on Tuesday, Boston media quoted a Chinese Consulate General official as saying Chinese national Lu Lingzi was missing in the wake of Monday's bombings.
All three victims were young. None were running in the race. All were there, at the finish line, to cheer on the participants or greet relatives or friends.
The youngest of them was third-grader Martin Richard, of the Boston suburb of Dorchester.
A year ago, as part of a class peace walk, Martin had marched with his classmates to Boston city hall. A photo from that occasion went viral Tuesday. In it, Martin is holding up a cardboard sign that he made. Next to two hearts, it said: "No more hurting people. Peace."
On Monday, Martin, a soccer player, was near the finish line with his family and had just hugged his father, Bill, the Boston Globe reported. In a statement, Mr. Richard said his wife and a daughter are "recovering from serious injuries" and said the family wanted to grieve for their son in private.
The local NBC affiliate reported that Denise O'Brien Richard, Martin's mother, had surgery for a brain injury while the injured young daughter, Jane, might lose a leg. Martin's older brother, Henry, was uninjured.
Ms. Campbell, a 29-year-old steakhouse manager, came to Copley Square with a friend, Karen Rand, to take a picture of Ms. Rand's boyfriend, who was taking part in the race. Then the bombs went off and for hours there was no news of the two women.
"Worrying like crazy about … Karen, who was in the area where one of the bombs went off at the marathon. Phone lines are down and we can't reach her," her sister-in-law, Cheryl Rand Engelhardt, wrote on Facebook.
The detonation had broken Ms. Rand's left leg and severed an artery. Her eardrums were also broken. She underwent surgery at Boston's Massachusetts General Hospital.
According to her sister-in-law, Ms. Rand was carrying Ms. Campbell's identification papers so that when she came out of surgery, the hospital thought she was her friend.
Ms. Campbell's father, William, had been told that his daughter might lose a leg. He was stunned when instead of his daughter he saw Ms. Rand in the hospital bed, her grandmother told CNN, adding that officials would only show him a photo of his daughter to confirm the young woman's death.
Mr. Campbell told the Associated Press that his daughter was a "very caring, very loving person, and was daddy's little girl."
Editor's Note: An earlier version of this article incorrectly said that Bill Richard ran in the marathon. He was a spectator.