I am blaming the communist organization “ANTIFA” for this until told otherwise.
vegan ping
Anhydrous ammonia is used in older cooling equipment(milk cooler?) and could explode, but we are talking a 25% in air mixture explosive/flammable range and that was a big kaboom. I guess this scenario is possible, I’m not sure, just an idea or maybe propane gas, being used to heat all or part of the building, leaked out of piping eventually filling the building, creating a large explosive atmosphere. (Old-old FD Hazmat guy)