At a news conference Friday evening, Los Angeles Police Chief Charlie Beck identified the suspects as Bryan Barnes, 20, of Los Angeles and Javier Bolden, 19. Barnes was taken into custody Friday afternoon by a team of LAPD SWAT officers, along with FBI and other federal agents, who raided an apartment near the USC campus. Bolden was arrested by the same team three hours later in Victorville and flown back to L.A. by helicopter.

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.

The cellphone of one of two USC graduate students slain last month helped lead police to their alleged killers, law enforcement sources told The Times.

Beck offered few details about the arrests. But police sources, who requested anonymity because they were not authorized to speak publicly about the ongoing investigation, said Barnes was the suspected gunman in the April 11 slaying of electronic engineering students Ming Qu and Ying Wu, both 23.Bolden was believed to have been present when the students were gunned down during a robbery while sitting in Qu's parked BMW in the 2700 block of Raymond Avenue, the sources said.The suspects were being held without bail and were expected to be booked on suspicion of murder late Friday. They are scheduled to be arraigned Tuesday.Beck said the suspects did not have extensive criminal records but were believed to have been involved in two earlier attempted slayings."Early on, forensic evidence made us suspect quite strongly that this was a part of a series of crimes committed by the same men," the chief said.Ballistics tests on shell casings recovered at the scene of the shooting show they were fired from the same gun used in two other shootings, police sources said.

Detectives working on the two previous shootings had followed some "very tenuous" leads that they believed tied the earlier incidents to the primary suspect in the USC case, a police source said.

Beck and Mayor Antonio Villaraigosa praised detectives for their work.

Villaraigoisa portrayed the arrests as a sign of how seriously the city takes public safety and sought to reassure an international audience, in Spanish and English, that Los Angeles is not a dangerous destination.

"Safety is priority No. 1 in this city," he said. "Students at our city's universities should feel safe in and around our campuses."

The mayor, the father of a college-age daughter, said his heart went out to the Chinese students' parents.

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-- Joel Rubin and Lisa Girion

Photo: USC President C.L. Max Nikias bows before images of Ying Wu and Ming Qu before eulogizing the students at a memorial service last month. Credit: Luis Sinco / Los Angeles Times