On a gorgeous spring day, Lu Lingzi and two fellow Boston University students ventured to the finish line of the Boston Marathon to observe one of the most storied traditions of their adopted city. Lu was from Shen­yang, one of the largest cities in northeastern China, and had moved last year to Boston, a city brimming with students and youthful energy. Before heading out that morning, she posted online a photo of a fruit salad she called “my wonderful breakfast.”

“She was very enthusiastic,” said Tasso J. Kaper, chairman of the BU mathematics and statistics department, where Lu was a graduate student. “The tulip trees were in bloom. The Bradford pear trees were in bloom. It was a very exciting time to be in Boston.”

But the tradition was cut short by two explosions. When Lu didn’t return home Monday evening, Kaper said, her roommate began frantically looking for her. As the hours passed, more and more friends and classmates became panicked. Newspapers and Web sites in China posted her photo seeking information.

One of the three friends at the race was not injured. Another, Danling Zhou, a graduate student of actuarial science from Chengdu, in China’s Sichuan province, was critically injured but is in “stable condition” following surgeries Monday and Tuesday, according to the university.

On Wednesday afternoon, BU officials said they had received permission from Lu’s family to announce that she was one of the three killed in the explosions. The university initially released an Americanized version of her name but later switched to the Chinese version.

Boston University confirmed Wednesday that Lingzi Lu, who was studying mathematics and statistics at the school and was due to receive her graduate degree in 2015, was among the people killed Monday. (AP)

As flowers piled up at makeshift memorials in Boston, Weibo, a Chinese Web site similar to Twitter, lit up with thousands of condolences and digital candles.

“Can’t God hear the prayer of so many people? Why make so many people heart-broken? I wish it were a dream,” wrote one university schoolmate using the Weibo identification “Vera Yu Yuanyuan.”

Li Chengpeng, a columnist, wrote on Weibo: “Please light candles for her and let her rest. Twelve years after 9/11, more and more people have realized that terrorism is the global enemy. They don’t distinguish nationalities and races.”

Lu, an only child, graduated from Shen­yang’s well-regarded Northeast Yucai School in 2008, then studied economics and international trade at the Beijing Institute of Technology.

“She was a very industrious and positive student,” said one of her Beijing English teachers, who asked not to be identified by name. He said on Wednesday that he looked back at the e-mails from her that he had kept with revisions of her papers. “Her writing ability improved very fast in a short time,” he said, “and she had her own ideas on many issues.”

In 2010, she attended a three-month program offered by the University of California at Riverside that allows foreign students to earn U.S. college credit and increase their chances of getting into graduate school. Lu was fluent in English, according to a UCR spokeswoman, and several students in her program continued onto Boston University.

Lu started her graduate classes last fall. Kaper said that the department’s professors carefully watch foreign students to ensure they properly adjust to their course loads and life in a new place. Lu had no problem with that, he said, and quickly became the leader of her social circle.

“She was sweet and nice,” said Lu Zhang, a fellow graduate student who had trouble speaking about Lu without becoming emotional.

Kaper added more adjectives to the list: smart, engaged, bubbly and “very, very happy.” Lu quickly proved herself “an outstanding student,” he said, performing “very well” in her courses. She had applied for fall internships, showing an interest in working in finance.

“She was well on her way,” Kaper said. “This was someone who was basking in the glory of success. . . . It’s a senseless loss of a young statistician. And in the most insidious way.”

Mufson reported from Beijing. Post researcher Zhang Jie in Beijing, and Caitlin Dewey, Jennifer Jenkins, T. Rees Shapiro and Debbi Wilgoren in Washington contributed to this report.