>> reporter: it is certainly what they're looking into. it can't go unnoticed that you have this tremendous tropical storm that was moving through the area at the same time you had this horrific accident. so clearly, that's where they'll begin. we're at the girls ranch where the heart break is heaviest. this is where eight of their children died. so now they're just beginning the grieving process. the investigation, ten ntsb investigators are now joining the efforts already underway by local and state law enforcement as they try to determine how it happened. so it was 2:30 on a saturday afternoon. if you've seen the images from the crash site, even the aftermath is chilling and horrific and it gives you a sense of what disastrous consequences took place. this was a multicar accident. what that means is that you had one vehicle begin. maybe it was hydroplaning. then another vehicle slams into it. the chain reaction begins. the horror as people try to get out of their vehicle, another