I didn't examine that closely, but — no. They seemed to just be people. Who had then become undead, through means which I cannot identify; no necromancer did that.

The water may have, it could have been infectious.

[ Harrow may have no idea where they came from, but it didn't stop her from keeping some of their bones. Just in case! It might be useful someday. And it makes her feel whole again, to have a collection. ]