You use the term "Evangelical Christian" as a matter of convenience for what purpose I don't know, but suspect it is not an endearing  one. A Christian is one who has the Spirit of Christ dwelling within them, trying to take the quantum leap of lumping a mass murderer/serial killer in with a person who is tempted and falls into Sin once in a while is a leap I cannot make, nor does it make logical sense. The guy you referenced was methodical and planned out his sins well in advance - Although I cannot prove it, I can't believe this guys was a Christian, it is inconsistent, the Bible makes it clear those who have a practiced "habit" of sinning cannot be counted as Children of God.