I was in the touring car attempting to figure out how the ring fit into all of this, and went so far as to decipher that the shadows were a distraction from the real killer. Unfortunately, before I could truly work on this theory I heard shouts of help from the observation car. I ran to investigate and found Jo being attacked. I zapped the invisible... guy, and used the currents to pinpoint his location. Jo, then, shot him. Not my preferred method of victory, but at least the killing might stop with his death.