Lu was one of three friends who watched the race from the finish line, the school said. Another friend, Zhou Danling, was injured when the bombs exploded and is in stable condition at Boston Medical Center.
Over a pizza lunch on Wednesday, the BU statistics department gathered for a tearful meeting over the news. Some students leaving the meeting cried and embraced.
[Updated at 11:41 a.m. PDT, April 17: Professors in BU’s mathematics and statistics department remembered Lu as an A student at the top of a tight-knit community. Many students worked on projects together and knew Lu well, they said.
Tasso Kaper, the chair of the mathematics and statistics department, said Lu was enthusiastic and energetic. Lu had begun to look into internships and had learned the day before the marathon that she passed a major exam required for her degree. She was on track to graduate next year.
“We lost a promising young scientist,” Kaper said.]
Originally from Shenyang in northeastern China, Lu was a top student at her high school and did well enough to attend the Beijing Institute of Technology.
"The girl is very smart," Yang Yongkun, a high school teacher, was quoted as saying in Chinese media. "Although she graduated some years ago, I still remember her."
Lu moved to Boston in August to get a master's degree in actuarial science, the study of risk. Her comments about her life on the microblogging website Weibo were cheerful and positive, focusing on the best aspects of her new life in the United States.
The morning of the bombing, Lu posted a photograph of a plate of bread and vegetables, next to a smiley face and a caption reading, "My wonderful breakfast!"
It was the middle of the night in China when the bombs exploded, so there was little immediate reaction. By midday Tuesday in China, midnight Monday night in Boston, Lingzi's parents and grandparents were panicked that she hadn't called.
"Lingzi, where are you now?" her roommate wrote on Weibo, noting that Lu had a poor sense of direction. "I know you get lost so easily. Don't worry. We will find you."
BU planned to hold a service of healing at Marsh Chapel on Wednesday at 5:30 p.m.
Times staff writer Andrew Tangel in Boston contributed to this report.