If somebody pulled out a gun on a crowded train you were riding on, would you notice? These people didn't.
Why? They were too into their smartphones, a San Francisco prosecutor says.
The September killing of 20-year-old Justin Valdez on that busy train was shocking enough. The shooter, apparently picking the victim at random, shot the San Francisco State University student in the back.
Also shocking, the prosecutor says, was the initial actions of bystanders. Or inaction.
"Some are no more than two to three feet to him," said San Francisco District Attorney George Gascon "We're seeing people that are so disconnected to their surroundings. This is not unique. People are being robbed, people are being hurt, people are being run over by cars because they're so disconnected because of these phones."
A suspect has been arrested for the killing and pleaded not guilty, authorities said. But the phenomenon of witnesses being distracted by technology may continue, Gascon said. CNN's Kyung Lah reports the latest.