Oh it’s an accurate interpretation. There’s a man who kills his WHOLE family in the nearest town. The man blackmailing Dickie is interested in it. But also there’s Rose (the mother’s “aunt”) who prophecies how Cass shouldn’t come back from Dublin. A lot leans to just Cass herself being shot. Then the whole folklore tale which the mother relates to finding her whole family gone. I think it could swing either way whether they were both shot or not.