The key so far has been a taxi cab driver who told officers he saw it all happen. 911 calls from witnesses just after the initial accident involving the dark blue Chevy Trailblazer can be heard loud and clear.
Dispatch: "Did you see it happen sir?"
Caller: "Yeah he just lost it. Just rolled that baby."
Another witness describes to a CHP dispatcher the low visibility conditions out on Highway 99 early that morning.
Caller: "There is a vehicle that has all of their lights off and all the way to the left lane, completely just parked in the middle of the freeway. Ohh they're flipped over? They're flipped over on their side right off the 99."
CHP officers say the driver of the trailblazer somehow lost control of the vehicle and swerved to the right. The driver then overcorrected and hit the median, trapping the three girls who were inside. In the released copy of the 911 calls, it wasn't until halfway through do we start hearing calls for the second crash involving the greyhound bus.
Caller: "I believe somebody is injured. There was an accident previously and a car was flipped over and i guess this bus didn't see the car was flipped. And then the bus ended up hitting that car that flipped and they went off the road."
Investigators say the bus was heading north, in the fast lane when it hit the SUV and then veered to the right, down and embankment into a tree.
A third vehicle, a Honda SUV had been alongside the bus, in the slow lane, and was forced off the highway by the bus. Three people died in the first SUV. The person inside the second SUV was injured. The bus driver and two passengers also died.
The best information is coming from the driver of a yellow taxi cab. Matt Coupland is lucky to be alive as he explained to CHP he was right next to the bus just seconds before the deadly crash.
"Just as I was getting to the slow lane, the bus was getting to the fast lane. Side by side at the same time. We were going up to the crest as soon as we went over the crest there was a car sitting on its side blacked out no lights no nothing and I just barely missed it he just broadsided it, exploded into pieces everywhere."
It's still not clear how the accident involving the trailblazer happened. It could take months for investigators to finish their report.