I don't see how the bus was going UP the hill. It went DOWN into some ravine. If it was going UP and missed the curve, it would have impacted the dirt hill on the high side and you could see it from the street. Hell, if it was going UP the hill, it would have blocked traffic because the dirt hill is not even 20' from the street, and there would have been new damage to the guardrails.
The EMT guys were going way ~down~ the ravine with stretchers. The bus wasn't in sight. I was right ~there~, stopped for a good 3-4 minutes before the bikes could get through.
I'd be quite surprised if it was anything besides failed brakes going downhill, with the bus going, at speed, straight down the ravine far enough to be hidden from view. But, who knows, I could be wrong...