Investigators believe the USC graduate student killed near campus last week may have tried to get away from his attackers after the beating began but was assaulted a second time, law enforcement sources said.
The sources, who were familiar with the investigation but not authorized to speak publicly, said there was evidence indicating Xinran Ji struggled with his attackers. The evidence, they said, also indicated the 24-year-old was beaten a second time after the initial assault.
A criminal complaint alleges that Garcia, Ochoa and Guerrero used a bat and a wrench in the attack.
The four are scheduled to be arraigned Tuesday afternoon.
Prosecutors have yet to decide whether to seek the death penalty against Garcia and DelCarmen. Ochoa and Guerrero are not subject to the death penalty because of their age, prosecutors said, and instead face life in prison without the possibility of parole if convicted.
Under California law, prosecutors have discretion in certain crimes, including murder, to charge a minor as an adult. The courts, however, have ruled that minors are not subject to the death penalty.
Ji, an engineering student from China, was attacked about 12:45 a.m. Thursday as he walked home from a study group. Despite a head injury, he managed to make his way back to his apartment a few blocks away, where a roommate later discovered his body.
Prosecutors allege that after attacking Ji, the suspects drove to Dockweiler Beach, where Ochoa, Garcia and Guerrero approached a man and woman. The three allegedly robbed the woman, but the man managed to escape and flag down police officers patrolling the area.
The complaint alleges that Garcia, Guerrero and Ochoa again used a bat at Dockweiler Beach and that Guerrero and Ochoa also used a knife.
Detectives believe a 14-year-old girl who was detained in connection with the Dockweiler Beach robbery also was involved in Ji's assault "in some manner," LAPD Cmdr. Andrew Smith said Monday, though the "detail and depth" of her alleged involvement was not clear.
Meanwhile, detectives with the Criminal Gang Homicide division who were investigating Ji's assault issued a department-wide bulletin for a vehicle sought in their case, the source said. The officers who impounded the vehicle in connection with the Dockweiler Beach robbery realized it matched that description, helping investigators link the two crimes.
Police said there were no indications the suspects were gang members or that the attack on Ji was racially motivated.
Detectives also said they believe the suspects may have committed other crimes Wednesday night or early Thursday, Smith said.
Law enforcement sources said security cameras and a license plate reader helped identify the suspects in Ji's death. USC Public Safety Chief John Thomas said the suspects were apparently not aware of the network of technology — including 150 cameras — scattered on and around campus.
Both the university and Los Angeles police amplified their security resources at the South L.A. campus and surrounding neighborhood after two Chinese graduate students were shot and killed in a botched robbery in 2012.
Six months later, a man opened fire outside an on-campus Halloween party, injuring four people, though none of those victims were students.