I have the theory that they were sort of creating a mysterious unknown character who was the only identity behind many things of the show that later (in some cases much later) we find out who the responsibles were... Taking the necklace, spying the deal between Leo and Mike and Bobby, attack Jacoby, maybe even shoot Coop... If you look closely all those characters are similarly dressed and their faces are masked (Coop says that about his shooter). Of course, as I say, later we are told that Josie shot Coop, that Jacoby took the necklace and that Leland/BOB attacked Jacoby, different people, but the pattern is there... If you see the series for the first time, but pay close attention it's understandable to think all those are one and the same...

But only based in what we know and not in the conjectures I'm talking about my guess is that person was supposed to be Jacoby, but this was never revealed... He tells Coop and Harry that the night after Laura died (the Pilot's night) he was following Leo, the man with the red Corvette Laura told him about... The night of episode 1, which is the same night we see in the next ep. when Leo meets with Snake and Bopper, he listens to the tape Laura recorded the day she died and he mentions a mystery man who "can really light my fire as in red Corvette" and that has tried to kill her a couple of times... She was obviously talking about BOB, but Jacoby once more remembered Leo's corvette and once more decided to follow him that night, this time into the woods... Leo didn't know someone was there...

I don't think that the shaded person who appears behind a tree when Mike and Bobby meet Leo is the same as the shaded person from later on in the series.

My sister and I use to theorize it was possibly Leo's gay lover. If you read Leo's ad in Flesh World it states that he may be bi.

I believe Leo's reaction indicated that he did know someone was there.

I always wondered about this, too. Leo knew who it was b/c he told Mike and Bobby not to worry about it when he was asked who it was.

When I read your responses, the gay lover thing sounded kind of silly at first but when you think about it, it isn't so far-fetched! At all. It would explain some of his menacing behavior toward Shelley (stress due to not being completely open with his sexuality).

 I wonder if it was Bernard??? (seriously)