Ask HN: Our startup has a Facebook page imposter – what to do?

To keep it brief - we noticed today that somebody has replicated our Facebook page (using the same name, profile picture & header which contain our trademarked logo). Of course we don't know who it was, but definitely not a team member at our startup. Anyone had a similar experience and know the best course of action to take? Apparently FB isn't very helpful in this kind of situation...