I didn't realize the werewolf's identity until the very end when the naked minister was dead on the living room floor. Then, I thought, "Aha! That's who Marty shot in the eye with a rocket earlier in the movie." Sure, we see the minister with a patch over his eye, but no direct confirmation that his eye was actually missing.
Nobody KNEW. And anyone who says otherwise is full of $hit. Up until the eye patch, there wasn't a single piece of evidence or clue that alluded or hinted the Preach was the werewolf. Taking a GUESS does not mean you KNEW.
First time I saw it, about 15 years ago, it was the scene where Reverend Lowe has his eye patch on that I thought it might be him. Now, I think there's a hint that it's him when he tries to stop the lynch mob. And of course there's his nightmare.....