They see captain sleeping, they panic. Why do you think this “tape”/pictures were taken if it’s so common pilots sleep while on duty? Why did he resign before the investigation?
In this incident there were no reports of pax 'panicking', in fact everyone seems to have been having a bit of a giggle about it. The DHC-6 does not have a cockpit door separating it from the cabin which is why the 'uncommon' footage was possible.
The Capt's resignation was announced by the airline General Manager in very short order. You can draw your own conclusion.
Other pax say he was awake for both the takeoff and landing and dozed for about 30 minutes at cruise, if in fact that
was what he was doing.
The real villain here ISTM is the venal pax who rushed his scoop to the nearest media outlet. Maybe there's something to be said for banning cameras after all