I've been keeping an eye on this, I find it very hard to believe the woman's leg was amputated BEFORE she was taken to hospital, as some sites are reporting, especially considering reports also suggest she stood up after the incident occurred.
What happened appears to have been massively exaggerated by the 'park worker' (who I expected is now unemployed, you don't talk to the press about an incident) and from the eyewitness reports from people who seem to actually understand how the laws of physics work, the boat came down the drop when the water level at the bottom was too low, and because of the weight it was unable to deccelerate quickly enough - which the water in the trough would do, acting as a brake - and so hit the corner too fast ejecting the riders.
A horrible thing to happen and I hope both injured riders get better soon... But it's hard to say who, if anyone, is at fault here or if it was just one of those freak incidents.