Jonathan Del Carmen, 19, Andrew Garcia, 18, Alberto Ochoa, 17, and Alejandra Guerrero, 16, were charged with the capital murder of Xinran Ji.
Ji, 24, was a graduate student studying engineering at the University of Southern California. Investigators said the four attempted to rob him as he walked home from a study group just after midnight Thursday.
Ji returned to his apartment after the assault and died there. His roommate later discovered the body.
Investigators said that Ochoa, Garcia and Guerrero tried to rob a man and woman in Dockweiler Beach after the Ji attack. The man was able to get away and summon police, and Guerrero and a 14-year-old girl were arrested.
The other three were arrested later and their vehicle seized. They became suspects in Ji's killing when detectives investigating the Dockweiler Beach robbery noticed the vehicle's description matched one put out by their colleagues.
Police have said they believe the 14-year-old was involved in the attack on Ji, although they are unsure of her role.
Del Carmen and Garcia could face the death penalty, although prosecutors have made no decision on seeking it. Guerrero and Ochoa could be sentenced to life with no parole.