Exactly four years ago this morning, the Bay Area was riveted when Asiana Airlines Flight 214 clipped a seawall at the southern lip of the main runway at San Francisco International Airport and crashed on the tarmac. The fiery wreck claimed three lives, all of them teenage girls from China, including one who was accidentally run over by a rescue vehicle after she’d been covered in fire-fighting foam. Some 187 passengers were injured. Related Articles Asiana Airlines’ perplexing response to Flight 214 crash

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This week, a previously unpublicized video of the crash and its aftermath turned up on social media. And while airport officials confirmed the authenticity of the video, it was unknown how it surfaced. The video, which has a “Don’t distribute” stamp on it, was apparently taken by an airport camera on a tower roof.

The dramatic video runs for 47 minutes, without sound, and offers a front-seat view of the 2013 crash, fire and evacuation of the jetliner. In the opening sequence, the Boeing 777 makes its approach from the south as it ends its voyage from Seoul, South Korea. After its landing gear strikes the seawall and the aircraft slides to a stop, it’s engulfed in clouds of white and black smoke. Passengers quickly begin escaping on inflatable slides as firefighters respond and turn their hoses onto the burning plane.

The video, say authorities, was previously used by investigators and as a safety-training tool, but airport officials could not say how it ended up being posted online four years after the tragedy took place.