Passengers on San Francisco's Muni train were so focused on their smartphones that they didn't notice a man drawing and pointing his gun until he shot university student Justin Valdez, District Attorney George Gascón says. As SFGate reports, security footage from September 23rd captured "dozens" of passengers apparently ignoring a man who drew a .45-caliber pistol several times, pointed it across the aisle, and eventually shot Valdez as he stepped off the train. "These weren't concealed movements — the gun is very clear," Gascón told SFGate. "These people are in very close proximity with him, and nobody sees this. They're just so engrossed, texting and reading and whatnot. They're completely oblivious of their surroundings."

The shooter was allegedly Nikhom Thephakaysone, who has since been arrested. But Gascón said that although cellphones help people document and report crimes, they created a kind of bystander apathy in this case. It's not clear how full the train was, although dozens of people would add up to a crowded car. Multiple reports have cited "distracted walking" — while using a smartphone or other device — as a cause of increased accidents, just as cell use while driving has been deemed a potentially fatal risk. On subways, though, other factors could also make people less likely to spot warning signs. Phones aren't inherently more distracting than books or newspapers, and looking too closely at passengers on a crowded train is often considered taboo — in this case, it's also not clear how much it would have helped. As the video hasn't been released, we're left only with Gascón's warning that a busy screen can add up to a deadly distraction.