Epic Latin Question

[dtewi]

(NOTE: Only for people who have taken at least a year of Latin)

Well, on my homework this sentence came up:

"Do they know who had been taken by the common people?"

At first, I wanted to use the relative pronoun, so it was this:

"Sciuntne qui ab vulgo captus erat."

But I was stumped, as I had no clue what the antecedent was and couldn't form the sentence correctly.

The interrogative pronouns was what I thought next:

"Sciuntne quem ab vulgo captus erat."

But that doesn't make sense.

Then I threw my pen down and just stopped writing.

Another thought I had was "who" had a double loyalty, being both an interrogative and relative pronoun, but I have no clue how'd that make sense.

Help?