LOS ANGELES (AP) — A graduate student arrested on suspicion of stabbing to death the professor who oversaw his work at the University of Southern California was being held on $1 million bail Saturday as their shocked colleagues began processing the news.
David Jonathan Brown, a 28-year-old brain and cognitive science student, was arrested in the Friday afternoon attack in the heart of the Los Angeles campus. His mentor, Bosco Tjan, was killed inside the Seeley G. Mudd building, where he runs an intensive lab that studies vision loss.
Brown, one of just five students who worked in the lab, was arrested without incident almost immediately afterward, police said, adding that the killing was targeted. In a biography page about the lab and the students involved in it, Brown’s is the only one without a detailed description or photograph.
Nathaniel Kwok, who recently finished working 18 months in the lab, said graduate students like Brown work in the lab 40 to 60 hours a week and develop their own projects that are required in order to graduate.
Brown had been working in the lab since around 2013, but he took a leave of absence for personal reasons sometime last year that lasted roughly a semester, Kwok said. He added that he didn’t know why Brown needed the time off or how close to graduation he was.
“He seemed normal for the most part. He was a little on the reserved side, but he was nice. He was friendly,” Kwok said from New York, where he’s now in medical school. “There was nothing that ever would have given me some kind of indicator that he would be harboring any kind of sentiment like this.”
Brown said Tjan treated him as a son and that he always loved the professor’s frankness, sarcastic wit and sharp mind.
Kilho Shin, a brain and cognitive science graduate student who works in Tjan’s lab, said Brown was a quiet student and seemed satisfied with Tjan’s oversight.
“I don’t know what exactly happened between them. But as far as I know, Bosco likes David’s work and David also seemed to be satisfied with his supervising,” Shin said. “Their conversation on research was healthy and constructive.”
Shin said he was shocked by Tjan’s killing, adding that the professor was humorous, kind and warm, and a genius in his area of study.
“It is a big loss not only to me but also in this field and society. He has served his lab members as his family members, not just graduate students, including David Brown,” he said.
Chris Purington, project manager at Tjan’s lab, said Friday that he never heard of anyone having a problem with Tjan, a married father of one son listed in public records as 50 years old.
“He was somebody who really cared about people. I know he cared about me,” Purington said through tears. “He mentored people, and he looked out for them. He spent a lot of time thinking about what it means to be a mentor and guide people.”
Purington, who traveled with Tjan for various science conferences, said everyone knew and loved the professor.
“People talk about scientists as very cold or robotic. Bosco is a guy that he could talk to anybody about anything,” he said. “He couldn’t move through a room without being sidetracked in all these conversations.
“He just had this energy about him. Kinetic might be the word,” he said. “He had a huge impact on my life.”
Purington, who also oversaw Brown at the lab, said Saturday that he was not ready to speak about the student.
David Clewett said he was a student in Tjan’s brain-imaging course and met with him about how to analyze his data.
“He was a brilliant scientist and an exceptional person who was always kind, generous with his time, and genuinely cared about his students and colleagues,” Clewett said. “This is such a tragic and shocking loss.”
In a letter addressed to the USC community, university President C. L. Max Nikias called Tjan’s killing a tragedy.
“As the Trojan family mourns Professor Tjan’s untimely passing, we will keep his family in our thoughts,” Nikias said.
Tjan joined USC in 2001, taught in the Dornsife College of Letters, Arts and Sciences, and served as co-director of the Dornsife Cognitive Neuroimaging Center, Nikias said.
The stabbing comes six months after a well-loved professor was fatally shot on the nearby UCLA campus. Authorities believe former student Mainak Sarkar killed his estranged wife in a Minneapolis suburb before driving across the country to Los Angeles and fatally shooting engineering professor William Klug before killing himself on June 1. Klug had helped Sarkar earn his engineering Ph.D. in 2013.