Despite a demanding schedule that included teaching, research and overseas travel, Bosco Tjan always found time to sit down with his students – usually over a cappuccino.

The professor of psychology had an affinity for coffee, sometimes drinking seven espressos per day.

Helga Mazyar, a doctoral student in neuroscience, enjoyed many intimate conversations with Tjan, her mentor over the past five years.

Mazyar described Tjan as both a pioneer in his field and a beloved professor who truly cared about his students' success. She was among the hundreds of people who attended a vigil honoring Tjan in USC's Hahn Plaza on Monday.

"He cared about my personal life as much as he cared about my academic progress," Mazyar said. "I could talk to him about anything and he could always listen and offer his best help."

Mazyar said Tjan went out of his way to lend others a helping hand. When her car broke down a couple months ago, Tjan referred her to a mechanic and offered tips to ensure the mechanic did a good job.

As Tjan's colleagues and friends recalled the professor's caring personality and affable demeanor, they all grappled with the same question: how could a man adored by so many students see his life end at the hands of one?

Tjan, 50, was fatally stabbed Friday afternoon inside USC's Seeley G. Mudd building, according to the Los Angeles Police Department. David Jonathan Brown, a 28-year-old doctoral student who worked in Tjan's lab, was arrested on suspicion of murder.

Tjan's sudden death sent shockwaves through USC, where he had worked as a professor for 15 years and co-directed the Dornsife Cognitive Neuroimaging Center.

USC President C. L. Max Nikias described Tjan as “a person who embodied many of our deepest values.” (Alan Mittelstaedt for Annenberg Media)
USC President C. L. Max Nikias described Tjan as “a person who embodied many of our deepest values.” (Alan Mittelstaedt for Annenberg Media)

USC President C. L. Max Nikias praised Tjan, whose research focused on visual perception and cognition, as "a giant within the academy."

"He has been a beloved mentor, a talented colleague, a dear friend, a man who made so many lives better," Nikias said at Monday's vigil. "Our sorrow and our anger are real, yet let us also be ever mindful of the enduring nature of his contributions to his field."

Tjan specialized in research of the human visual system, including facial recognition and vision cognition. His lab used computer simulations and neuroimaging to make contributions in these disciplines, and he won millions of dollars in grants from the National Eye Institute and the National Science Foundation.

Tjan's longtime colleague and USC professor of neuroscience Irving Biederman said Tjan earned deep respect in his field – both for his sharp intellect and his eagerness to assist others.

"It was no surprise that Bosco was a frequent invitee to conferences all over the world," Biederman said. "People wanted to hear what Bosco would say about their work."

Despite Tjan's impressive pedigree, he remained humble and phrased his criticisms gently, endearing himself to everyone he met, Biederman said.

"The quality of our lives at USC will surely be diminished by Bosco's absence, but we need to remember and celebrate the joy that his life did bring to so many of us," he said.

Remembering Prof. Bosco Tjan, 2016

Born in Beijing and raised in Hong Kong, Tjan emigrated to the U.S. with his family as a teenager, according to Bill Nguyen, a family friend.

Tjan received his doctorate in computer and information sciences from the University of Minnesota in 1997, where he met his wife Carissa, then an undergraduate majoring in chemical engineering.

Bosco and Carissa married and moved to Southern California shortly before Tjan started working as an assistant professor at USC in 2001. They had a son, who is now 9.

On Sunday, Nguyen and other friends from their days together at the University of Minnesota, gathered in front of Tjan's modest, ranch-style home in Cerritos. They drank warm coffee as they waited for Carissa to return home from making her husband's funeral arrangements. They began processing the unimaginable horror of what had occurred.

"He was a very nice guy," Nguyen said.

Reach Special Projects Editor Maral Tavitian here, and follow her on Twitter here.

Senior News Editor James Tyner and Staff Reporter Cole Sullivan contributed to this report.