In the crime scene photo Mulder shows the "Reverend" Orison, there's far too much blood to have come from a single victim, even allowing for displacement, and the perpetrator hadn't had time to dispatch further victims.
Scully states that the song "Don't Look Any Further" is one she hasn't heard since high school, but this song was released in 1984, making her 20 years old at the time (born in 1964 according to her FBI profile). She was out of high school and in college by this time.