n recent decades, supernatural beings bearing firearms have been within the purview of such narratives as the movie Legion and the comic book Preacher. But the idea of angels and devils locking and loading has had a much longer artistic heritage, dating back at least five centuries.
The top portion of Swiss printer Johann Amerbach's 1489 woodcut De Civitate Dei sees St. Augustine diligently at work at his desk, but it is the bottom half that deserves the Slayer soundtrack.
As John Ptak of Ptak Science Books notes of this tableau, it is "a battle between the cities of Babylon (founded by Abel) and Zion ('Syon,' by Cain). In this battle Zion is defended by devils, and the devils are armed." (In case this demon with a firearm is eluding your view, he's on the lower-right, beneath the monster with the stone/hardboiled egg with malevolent intentions.)
As for the angels, they would flex their own divine artillery against some demons in Celifodina's Scripturae Thesaurus in this 1510 printing by B. M. Lantzberg. (This scene is giving me more of a Helloween vibe.) Sure, the Citadel of Heaven may have cannons, but the heavenly host needs to work on their aim. For more fine moments in late medieval art, see the butt trumpet of the 1350s.