Tjan was a professor of psychology at the USC Dornsife College of Letters, Arts & Sciences. According to a USC website, his laboratory was devoted to studying the human visual system.
The Los Angeles police said that Tjan was fatally stabbed in the chest by a student who was taken into custody. Tjan's body was inside the Seeley G. Mudd Building in the southwest corner of campus.
The student's name has not been released, and police have provided few details about what happened.
Tjan came to USC in 2001 as an assistant professor and became an associate professor in 2008, according to his LinkedIn profile. In 2014, he was made a professor. He earned a PhD in computer science from the University of Minnesota.
USC said he was also a member of the Society for Neuroscience and Vision Sciences Society.
On LinkedIn, Tjan described his work this way: "My group studies the human visual system using a broad range of behavioral, computational, and neural imaging techniques to address basic and translational questions pertaining to vision loss, restoration, and rehabilitation."
Tjan and his colleagues looked into causes of impaired vision and potential rehabilitation methods.
"As the Trojan family mourns professor Tjan's untimely passing, we will keep his family in our thoughts," USC President C.L. Max Nikias said in a prepared statement Friday evening.
Times staff writer Shelby Grad contributed to this report.