Three Chinese friends from Boston University went to sample American life at the city's ill-fated marathon. Lu Lingzi was killed, Zhou Danling was badly hurt and the third wonders how she survived unscathed.
The whole campus has been scarred by the death of Lu, a brilliant rising mathematician, who only arrived at Boston in September, but had immediately launched into life at the prestigious institution.
The three women were among hundreds of people caught in the blast of two bombs that erupted at the finish line, killing three and wounding about 180.
Math department administrator Kathleen Heavey said many students had taken the news badly. "Some of them are handling it OK, and others are beyond control."
"Our hearts and thoughts go out to the family and friends of both victims," said Robert Brown, president of the university with more than 31,000 students from 100 countries.
A host of ceremonies and tributes have been organized. A mass memorial will be held on Thursday.
Lu and Zhou were among hundreds of Chinese students now in Boston.
Before going to the marathon, Lu posted a picture of her breakfast of Chinese-style dough and fruit on the Chinese social media website Weibo. "My wonderful breakfast," she commented in English.
Students organized desperate searches for Lu when it was discovered she was missing on Monday night. Zhou has undergone several operations in hospital and was said to be in "stable" condition.
"She has her friends around her, and she will soon have family around her," university chapel dean Reverend Robert Hill said in a statement.
The third girl has remained anonymous, too distraught to talk, students said.
Gao Qin, a 24-year-old law school student from Shanghai, said "everybody was worried about, everybody was trying to find this girl" when it was discovered Lu was missing.
"Everybody was shocked and sad" when they found out she died, Gao added.
"A lot of my friends were her friends, because it's a very small community. They remember what a fun and lovely girl she was, she was also working very hard."
Lu went to school in Shenyang and then earned a degree in economics and international trade at Beijing Institute of Technology. In 2010, she went to the University of California at Riverside for three months to boost her chances of getting a place on a graduate course.
Boston professors considered her a "brilliant" student, her counterparts said.
Theology student Meghan Nelson left a pair of running shoes, flowers and a university key chain in front of a memorial to Martin Luther King as a tribute to the killed student.
Joy Lin, a 23-year-old from Beijing, left a green hat and a note saying: "From Boston and Beijing with love."
"She was Chinese, and I'm Chinese. The hat captures Boston. A lot of Irish immigrants came here. Boston is my home. I love it so much," she said.
Several Boston University students witnessed the bombs and some were volunteers at the event.
Derrick Kwok was meant to help exhausted runners to a medical tent near the finish line. But in a dramatic twist, he had to switch to vacating beds to make room for victims who were covered in blood.
Another volunteer, Alex Kwok, said he and some of his colleagues felt both explosions, but they thought a tent had collapsed or that a generator had failed.
"I don't believe that a bomb was the first thing on anyone's mind," he said.