Mountain Life Flight Crash?

A Mountain Lifelight helicopter flight was on its way back from transporting a patient to a Reno hospital crashed this morning, killing all 3 crewmembers on board. The crash happened around 2am, near the California-Nevada border.
Apparently the pilot was not communicating with air traffic controllers at the time of the crash.
What caused the accident? Why did the helicopter crash?

The aircraft was destroyed in the crash and fire.
Sources say the cause of the fatal accident has not yet been determined. The FAA and National Transportation Safety Board investigators investigate the scene today in hopes of finding some answers as to why the medical helicopter went down.
The helicopter was operated by Mountain Lifeflight out of Susanville, Gregor said. The company issued a brief statement confirming the loss of all three crew members aboard the helicopter.

The pilot died in the crash and two crew members were seriously injured.

All 3 crew members, one of which was a very close friend of mine, were killed in the accident. So to the guy who posted that only the pilot was killed, please check your facts before posting them on a publicly accessible website.