This was discussed on a recent "No Agenda" Podcast. Adam Curry is licensed to fly helicopters and claims to have flown this model. He is insistent that this explanation is wrong, that the lever pictured controls ignition retard and is easily overridden by controls on the stick the pilot uses to control the aircraft.

It makes no sense to me that there would be a fuel shutoff in reach of a passenger that could cause the aircraft to crash. (Imagine telling passengers "whatever you do,, don't pull this lever or we'll all die.")

With the small size of a helicopter and passengers in the front seat, they are certainly in range of many controls which could have that effect.

I'm not familiar with the particular model of aircraft that crashed. But I've ridden in a cozy two-seater. As someone with zero piloting experience it seemed like it would have been easy to change all kinds of important controls, especially if it was an excited, inattentive person of the selfie snapping variety.