Mere speculation of course, but it seems a small step to me--from God's so-called Jihad avenger to assuming a God-like personna for one's self.
The jihadists like to think they are killing the enemies of God (phrase appears on their videotapes and in their literature.) I think we can assume none of the sniper's victims are Moslems, or the media would have been quick to tell us.
By the way, there's a big Moslem presence in Montgomery and PG Counties. I have eaten in halal restaurants there.