My guess would be that there was a large regional conflict, and refugees from many areas gathered in one camp (maybe a sanctuary or a neutral area). They maybe whoever killed them realized afterward that not all of them were from their intended enemies.
This is puzzling me:
I couldn’t find a single good explanation for all three things. Specially the last one, it seems contradictory.
My guess would be that there was a large regional conflict, and refugees from many areas gathered in one camp (maybe a sanctuary or a neutral area). They maybe whoever killed them realized afterward that not all of them were from their intended enemies.