LOS ANGELES » The messages in Chinese kept flashing across Haowang Wang’s phone: Another Chinese student at the University of Southern California had been killed.

Shui? Shui? the messages repeated. Who is it?

Wang froze briefly, then began making calls he thought he’d never have to make again — to friends, classmates, a funeral home.

Two years ago, he and others helped guide Chinese students as they grappled with the murder of two USC graduate students. They tried as best they could to navigate the foreign world beyond the cocoon of the university.

Now, he must do it again.

"Yinggai de," Wang said. "It must be done."

The killing of 24-year-old Xinran Ji on July 24 has drawn the community of Chinese students into a circle of sadness and confusion.

Ji, an engineering graduate student, was beaten to death with a baseball bat as he walked home from a study group after midnight, police said. Four teenagers have been arrested and charged with his murder.

The students, as scholars, are the cream of their country — the very smartest in a land of 1.3 billion people. But the killing of their classmate has thrown them into a foreign world that they must struggle to understand, just as they did two years ago.

The courts here move at a snail’s pace compared with China, where a trial and death sentence can be carried out in a few months. Even the most basic legal concepts here — innocent until proven guilty — are foreign.

Unlike students from Taiwan and Hong Kong, the students from mainland China are more recent arrivals and are culturally distinct. They have a powerful sense of obligation to bear witness for their classmates’ families in China, thousands of miles away.

"He was their only child," Wang said after contacting Ji’s family a few days ago. "I can understand their pain, their confusion."

Hundreds of students had gathered around the statue of Tommy Trojan two years ago to mourn Ming Qu and Ying Wu.

Qu and Wu, both 23, were graduate students in electrical engineering. Qu had just called his parents in China to tell them he was in love.

The couple were shot to death by two men as they sat in a parked BMW just west of campus. The motive was robbery, police said.

At the impromptu memorial, mourners with black hair and black clothing clutched bouquets of white lilies. They arranged white candles in the shape of a heart.

Some students nodded to one another, recognizing familiar faces on the way to and from laboratories, the library, the same off-campus streets.

How long have you been here? Where is your family from? they whispered to each other. The answers wafted across the gathering: Fujian, Hangzhou, Beijing, Yunnan and other places across China.

They could recognize one another by their accents, the way they dressed, their dreams to succeed in America.

For the more than 3,000 Chinese students at the university, their lives are joined by more than being strangers in a foreign country.

They are united by a childhood defined by the pressure to excel in school, to earn back the life savings their parents have invested in their wants and ambitions. Their lives are dominated by the Chinese government’s policy of allowing families to have only one child.

With each birthday and graduation, they are reminded that they are their parents’ one hope for the future.

They saw in Qu and Wu a reflection of themselves. The condolences they wrote in a book for their parents could’ve been said for any of their peers.

At the time, Wang was an engineering graduate student at USC and the president of the Southwest Chinese Student and Scholars Association. The group’s biggest activities involved organizing dinners and Chinese New Year celebrations for those who couldn’t go home.

Wang had come to the U.S. from the small city of Jincheng in Shanxi province. His mother was a retired accountant; his father, a businessman. Wang wanted to come to the U.S. "to open my eyes."

After the arrests of two suspects, Javier Bolden, then 19, and Bryan Barnes, then 20, Wang was worried that there would be no one to speak for Qu and Wu.

In a county with about 600 killings a year, who would fight for two Chinese students?

"We just want everybody to focus on the case, see how senseless the killings were," said Joy Xing, a close friend of the couple and a USC student. "I want to be there to show the court and society that my friends are not alone in this country."

The American criminal justice system is largely a mystery to the Chinese students.

Attorney Daniel Deng, who became an unofficial adviser to the students, said most do not understand that a suspect’s fate is decided by a jury of ordinary citizens, rather than professional jurors as it’s done in China.

"In China, prosecution to execution usually takes three to six months," said Deng, who came to the United States from China as a student 27 years ago. "Here, it’s not going to happen overnight. I explained to them the concept of due process, that the defense has the right to review the case."

The students began a courtroom vigil. No matter what, someone would sit in court each time, even though it was difficult to understand what was taking place.

At an early hearing, one student typed a quick search on his iPhone: "arraignment." He turned to some friends and confirmed in Mandarin, "They have to plead not guilty or guilty today."

"So if they plead not guilty, will the jury then come out?" asked Thomas Young, who had never set foot in an American courtroom before.

At one point, the students heard a rumor that Bolden and Barnes might get only 20 years in prison if convicted. That would be intolerable, they said.

They collected more than 7,000 signatures calling for the death penalty and demanded to see Steve Cooley, the district attorney at the time. Cooley explained the two outcomes that could come with the charges: The death penalty, or prison for life.

Earlier this year, Barnes pleaded guilty to two counts of first-degree murder. Under the deal, he avoided the death penalty and was sentenced to life in prison.

"My daughter is gone, so is our hope," said Wu’s father, Xiyong Wu, at the hearing.

He said he still logs on to his computer every day, messaging his daughter as if she was still abroad.

Bolden is set to stand trial at a later date.

Since the sentencing, many of the students who kept vigil in the courtroom have graduated and begun careers. Some have stayed here; many have moved back to China.

Ji’s slaying has reopened feelings they thought they had put behind.

At a memorial Friday, about 300 students gathered in Alfred Newman Recital Hall on campus. The students, some with white flowers in hand, walked into the hall. One by one they laid them on the stage.

Clusters of students huddled together, greeting one another in Chinese. Mourners bowed before a photo of Ji as his parents sat in the front row, occasionally sobbing.

Wang, who graduated from USC last year and stayed in L.A. to work on launching a job networking start-up, sat among the mourners. He’s been taking time off this week to talk with students about what to expect next.

Others have stepped up to help Ji’s family. They have begun a new courtroom vigil.

On Tuesday, Deng sat quietly at the front of the courtroom when the four teenagers appeared for arraignment. Next to him sat Sumo Liu, who just finished her first year at USC. They waited four hours, only to have the court proceeding postponed.

Liu was still in China when Qu and Wu were killed. Her parents didn’t want her to go to USC, but she decided to go because of the university’s academic ranking.

"I assumed after those two students, USC would do a better job with security, that it would be OK," Liu said. "Who would’ve thought it’d happen again? And for it to happen to my friend?"

Deng spoke this week with Qu and Wu’s parents. They were devastated when they heard about Ji, Deng said. They felt like they had failed somehow to make sure other students at USC were protected from their children’s fate.

"They just don’t want other families to go through the tragedy they have had to live through," Deng said.