— The young man, just 20, stepped off the train. Another man followed him, pulling out a gun. There was a single shot, startling the preoccupied commuters. Jason Valdez fell, gasping and screaming for help as he died, a bullet to his head.

That's according to authorities who have reviewed footage from a surveillance camera on the San Francisco Municipal Railway car on Sept. 23.

And what those videos also show, authorities say, is that the suspect Nikhom Thephakaysone, 30, had already pulled out his gun three of four times while aboard the crowded car, but the dozen passengers aboard were so hypnotized by their phones and tablets they failed to notice; not when he pointed the .45-caliber pistol across the aisle, nor even when he wiped his nose with the hand holding the gun.

"There are people facing in his direction, you can see them on smartphones and their tablets, highly distracted," District Attorney George Gascon told The Associated Press on Wednesday. "And you can see the suspect pulling the gun with his right hand, bringing it up to his face at least three or four times, parallel to his face and no one sees this going on."

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