Xinran Ji ran from his attackers, tearing along a residential street near USC when he was suddenly hit from behind.
A figure wielding what looked like a bat struck Ji in the head several times. Others joined in the beating, leaving the USC graduate student crumpled on the ground.
The attack, captured on surveillance footage by a security camera on a nearby building, was shown in court Tuesday as a prosecutor said that Ji was killed by four teenagers in an attempted robbery a few hundred feet from the campus.
The July 24, 2014, killing of the engineering student resulted in heightened security at the university and echoed the fatal shooting near campus of two graduate students in 2012. All three victims were from China, and the attacks prompted concerns back home about safety around the campus.
Tuesday marked the beginning of a preliminary hearing for three of the teens: Jonathan DelCarmen, 19; Alberto Ochoa, 17; and Alejandra Guerrero, 16. They are charged with murder and other crimes, including a robbery at Dockweiler State Beach a few hours after Ji's killing.
A trail of blood almost a quarter of a mile long stretched from the Orchard Avenue spot where Ji fell all the way to his home on West 30th Street. Police found blood on the sidewalks and streets, a mailbox, the button of an elevator in his building and the floor leading to his apartment.
A roommate found Ji's bloodied body in his bed the next morning. Most of his white clothing was stained with blood, LAPD Det. Matthew Courtney testified.
A security camera captured the beginning of the attack near the intersection of West 29th Street and Ellendale Place just after midnight as Ji was returning alone from a study session.
The footage shows a figure walking on the sidewalk when a car slows to a stop. Three people get out and confront the person, who then runs. The video is taken from a distance, and the figures are difficult to identify.
A second camera is clearer and shows Ji, wearing a backpack, running along Orchard Avenue when he is caught and beaten.
Claudia Rocha testified that she and a friend were at Dockweiler beach when they were attacked by a group of teenagers a few hours later.
She told the court that Guerrero threatened her with a pocket knife and Ochoa hit her friend with a baseball bat. DelCarmen, she said, was sitting in a nearby car to which two of the assailants ran. She said another teenage girl tried to snatch her purse, spilling money to the ground.
The preliminary hearing will continue Wednesday.
A fourth defendant, Andrew Garcia, 19, is also charged with murder and robbery. After an outburst by Garcia in court on Monday, a judge scheduled a Feb. 3 hearing to determine whether he is mentally competent to stand trial.
A teenage girl has been charged as a juvenile with robbery in connection with the Dockweiler Beach incident.
Times staff writer Sarah Parvini contributed to this report.