The issue will be (a) manufacturing a destructive device/ full auto. and (b) transfer of ownership of said weapon.
You can only manufacture when you have FFL as a Manufacturer, with the SOT to make the Class III NFA firearms. As far as (b), was ownership of the gun transferred? To who? As a Manufacturer, they can only transfer ownership to (1) a military agency, (2) a law enforcement agency, (3) to another FFL with the correct licenses/ SOTs. or (4) export it out of the US for legal sale abroad.
WAS there a transfer of ownership- or did the shooter shoot it in the presence of the Sons of Guns staff? If he works for Benelli, was it transferred to Benelli- who IS a FFL holder? etc etc. Bottom line- there is a lot you do not see with TV shows.
What we have here is... failure- to communicate.