It looks like it is in the descent (from the footage in flight). There is positive torque showing on the gauges and the PLs are in the green arc but they are very retarded from a cruise power position. Looking at the torque gauges they look to be displaying an appropriate TQ for a descent
There is also a positive airspeed on the FO PFD showing and the Nav Display is an 'in flight' nav display.
In addition, on the FWS, the Descent checklist is showing. This can be recalled manually but the ATR will automatically display this when the aircraft commences a descent.
So, I would say yes the aircraft was in flight ...
The question is, What the **** where the crew thinking or even the company to allow this?!
If the aircraft was descending then there certainly should have two pilots at the controls!