Skydriller,
he 'turned off one of the electronic systems and the engine stopped'
It's possible the pilot in question said to himself 'Look at that switch! I wonder what happens when I do this...' *dead silence firewall forward*.
The engine control units have a backup battery and runs off the alternator, even when no bus is powered.
However, if you turn off the Engine Master (which has a detent to prevent this) or the ECU that you have selected is turned off, the engine will stop.
So I suspect that incident was due to 'finger trouble'.
Deice,
An avionics type rating is a great idea!