brush fire cut visibility to almost zero. witnesses trapped in their cars were forced to watch powerless as the horror unfolded. trace gallagher live in l.a. with more. trace. >> reporter: and you have to remember, megyn, that when the rescue teams arrived on scene the smoke and the fog was so thick that they couldn't see. they had to listen for the screams and the moans of the victims and kind of feel their way around to find them. listen now to one of the 911 calls at the very beginning of this chain reaction crash, you'll hear how this tragedy gets progressively worse. listen. >> 911 what is the address of the emergency. >> um, i think we're on the 75, i75. >> yes. >> i can't see anything it's so dense, the fog is so dense i think we just hit a guardrail. i think there was another accident behind us because we heard it. >> another accident. oh, my gosh. >> what just happened, tell me