Two arrested in killing of USC students from China *

See update below

The LAPD says robbery was the motive for the April 11 killings of Ming Qu and Ying Wu as they sat in a car about a mile from the USC campus. Two men were arrested Friday, based at least in part on forensic evidence that apparently includes tying the gun used to at least two other recent crimes. The LA Times says an investigator described the case as "very, very strong" and that one of the suspects had been in possession of something that "could very readily be tied to one of the victims."

The suspects were identified as Bryan Barnes, 20, of South Los Angeles, and Javier Bolden, 19, of Palmdale. They were expected to both be charged with murder, although police believe one fired the shots and the other was present as part of the botched robbery.

Saturday update:Signals from a cellphone taken from one of the victims helped lead detectives to the suspects, the LA Times reports based on "law enforcement sources."

The sources said one of the suspects arrested Friday took a cellphone from one of the victims and detectives were able to locate him by tracking signals sent by the device.

Authorities also identified a signal from a second cellphone in proximity to the victim's phone, they said.

The second phone was identified as belonging to the suspect.

LAPD homicide detective Sal LaBarbera gives the Times kudos on Twitter for the story, but adds: "Man this big ships [sic] has leaks." He tweets later: "sometimes these Leaks are high above the bow line of the ship. Way high up. Just sayin."