According to various news reports a 44-year old man was taken in for medical treatment from Typhoon Lagoon on Saturday afternoon after an incident on the park’s newest attraction, Miss Adventure Falls. I'm not sure how it happened, but according to the reports his arm got stuck in the conveyor belt lift system at some point on the multi-passenger raft ride.
You know what they always say though, keep your arms and legs inside the ride vehicle at all times, so my best guess is that someone didn’t listen and unfortunately did something they shouldn’t have.