San Francisco authorities: Passengers on smartphones didn't notice man with gun before slaying

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 (Ni-KOM' tep-KAY'-sahn) 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.

The San Francisco Chronicle ( reported Monday that 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.