Adam. The box with the binoculars in they found in Matt's apartment after he was murdered had some sort of residue on it which Frankie (do you remember me...) identified as burn cream type stuff.
Yep it was Adam. The subsequent murders were set up to clear the girlfriend who took the rap for him and she was set up to look as though she had got the crucifix etc from The Shepherd. They did this because she had had previous psych probs. Then he discovered that the doctor's brother was jealous of hims and used him to get info on the other girls and to try to set up the doc or his brother