Now I'm sure some of you are already furiously typing on your keyboards "How could you think that?!? Where have you been this whole team?!? He's obviously Prometheus!" So just let me explain. I believe that Adrian Chase is Vigilante.
The character that Josh Segarra plays goes by the alias Adrian Chase, but that's not his real name. So is it possible that he stole someone else's identity? It would be kind of hard to rise up to District Attorney if your whole background is lie, even in Star City. My theory is that he stole the Adrian Chase identity and the man under the Vigilante mask is the real Adrian Chase. It wouldn't be the first time the Arrowverse has pulled this (Jay Garrick), and it would be a way of getting the redirect factor by having the guy you thought was Chase actually be Prometheus and stay true to the comic lore at the same time. Marc has confirmed that we know the person who is the true identity of Vigilante, so unless it's Paul I'm guessing that he's getting technical since we knew a Adrian Chase, just not THE Adrian Chase. Or maybe I'm just crazy. It's one of the two.