An ex Life Guard pilot in the same area as this accident happened. Among many flying jobs I have done, I believe air ambulance job is the most rewarding as well as demanding. Except some air ambulance operators in Canada which use Metro or B1900, almost all turboprop aircrafts in this industry are flown by single pilot. In some cargo operations, B1900 was approved for single pilot ops as well in the US as far as I know. So, it can be done. I am afraid the industry won't change their practice of single pilot in PC-12 after this accident, regardless of the finding of NTSB investigation.
It is easy to get pumped up and become too mission oriented in air ambulance ops. While we learned about the White Knight Syndrome of the early days of Medivac ops, it ain't easy to say "No, we can't take-off in this weather." to the flight nurses and patient, and his/her family who occasionally shows up to the airport.
Sad day, indeed.