Dam
Thought I had em there.
Actually pretty funny though, It is pretty hard to make shotgun powder actually explode with any force. It requires pressure to create greater pressure. The plastic bottles most of them are kept in do not provide such pressure.
Black powder requires less compression.
Flash powder will explode simply in quantity. The greater the quantity the bigger the explosion.
When I saw this the first time I read "an artist" as a musician so I thought of pyro shows.
Something still sounds fishy about this thing though. Smokeless powder is pretty hard to get a good explosion out of.
this must have been improperly stored or in such great quantity as to make the building the source of the pressure.