"Were they victims?"
Translation:Ĉu ili estis viktimoj?
I think in that context "victims" is an adjective, or it needs a preposition instead "Where they THE victims?" (victims is now a substantive) or instead "where they victims?" I understand victims is now an adjective, therefore "ĉu ili estis viktimaj?" should be the right answer.
I think it is a noun in the English sentence (and also should be in the Esperanto) I tried imagining what it was in Norwegian and in the totally similar sentence it was a noun. Ĉu ili estis viktimoj is a less ambiguous and thus arguably better sentence than
Ĉu ili estis viktimaj
viktimaj ranoj? viktimaj policanoj?