Indeed - a bolide crossing the city from northeast to southwest is by far the most plausible explanation, though, as the sky was clear, it would surely have bee

Indeed - a bolide crossing the city from northeast to southwest is by far the most plausible explanation, though, as the sky was clear, it would surely have been seen as a fireball, as in Chelyabinsk? Therefore, I would guess that the "bright streak" was coincident with the initial "roaring rumble", rather than following it, and the reports are conflating the passage of the fireball with its final explosion. If it caused the detonation or deflagration of the armory's gunpowder, that might account for most of the clouds, including trails of smoke from burning fragments thrown high into the air (the "messy strands of silk"?)