SAN FRANCISCO (CBS/AP) -- Investigators say a suspect in the random slaying of a university student flashed a gun several times on a crowded commuter train in San Francisco, but passengers were so absorbed in their phones and tablets they didn't notice.
Nikhom Thephakaysone is accused of fatally shooting 20-year-old Justin Valdez in the back of the head as Valdez exited the train. The 30-year-old Thephakaysone has pleaded not guilty to murder and other charges in the Sept. 23 slaying.
District Attorney George Gascon said passengers close to Thephakaysone didn't notice the gun because they were so engrossed in reading and texting.
Prosecutors have said he was looking for a victim and randomly chose Valdez. The moments before the shooting was captured on a train camera.
Valdez, a San Francisco resident, was originally from Garden Grove in Southern California.
He was shot around 9:50 p.m. as he left an eastbound Muni light-rail vehicle near Randolph and Bright streets, according to police. The M-Ocean View line stops at that corner.
San Francisco State University officials said Valdez was a sophomore who had started in the fall of 2012 and had not yet declared a major.
Valdez had attended Garden Grove High School and lived with his uncle, his high school principal Steve Osborne said.
Osborne recalled a "passionate and persistent" student who was the president of the school's environmental club and a top competitor in the Garden Grove High aquatics program.
While Valdez was a student, he would talk with Osborne frequently to see about changes to the school's recycling program, the principal said.
He also pushed tirelessly to establish a "Lights Out Wednesday" program to cut the school's carbon footprint, according to the principal.
"It's been devastating for teachers who knew him," Osborne said.
According to Valdez's Facebook page, he was a member of the SFSU Men's Club Water Polo team.
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