I'm thinking if he had like slightly higher ground towards a high so he's shooting just slightly downhill, and the hill is "too close", then he might feasibly shoot over it at a house behind it. So for instance the sights are supposed to be adjusted to 200 yards and the hill is somewhere around 100 yards away, then it would be about at the apex of the trajectory of a sight set for 200.

Ugh I don't remember it properly but when we shot with 7.62's in the army, iirc, the bullet arc was something like 30cm on a 150 or a 300m shot. I don't remember which.

Or maybe it was angled such that it was actually ricochets hitting the house or even rock fragments as bullets were obliterating bits of rock.

That would definitely make sense yeah. A loud boom and something hitting your building, you'd think someone is shooting at you sure enough.