San Francisco, CA : Twenty people critically injured tour bus crash on Friday November 13 2015

What began as a serene tour through one of the nation's most picturesque cities turned into a two-block ride of terror when an open-air tour bus careened wildly out of control in San Francisco's Union Square, running down a bicyclist, striking two pedestrians and smashing into several moving cars before it plowed into scaffolding lining a construction site.
Twenty people were hurt, six critically, when the big blue bus with at least 30 people aboard raced through one of the city's most popular tourist destinations Friday afternoon, leaving chaos and carnage in its wake.
Everybody was asking what's going on," said Bay Area resident Hoda Emam, who rounded a corner leading into Union Square moments after the bus struck the scaffolding, bringing it down in a twisted heap of metal and other debris.
She saw paramedics sprinting toward the injured while emergency vehicles pulled up with their sirens blaring.
Police officers were on top of the wrecked double-decker bus apparently attending to the injured, she said, while another three or four people lay in the street being treated.
There were still ambulances and fire trucks and paramedics with stretchers coming up," she said.
Twelve people suffered minor injuries in the crash that happened just before 3 p.m., San Francisco Fire Chief Joanne Hayes-White said. The others suffered moderate injuries.
Firefighters had to extricate the two pedestrians, who ended up trapped under the bus, and a passenger trapped on the upper deck.
The driver was conscious and able to speak when firefighters pulled him from the wreckage, Hayes-White said. But she added it was too early to speculate about what caused the crash.

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San Francisco tour bus crash injures 20