It turns out that the sound actually was tearing metal, specifically, the door of a car. It turns out, when you're a fifteen ton purple dinosaur, it's pretty easy to do that kind of thing, if you can find a few seconds where you're supernatural opponent is distracted.

The sudden reappearance of the Hound's master was just such a distraction and, while it wasn't enough time to get away, it was just enough time to grab a nearby jeep's door and hurl it down the street.

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