From the article:"Police said the assailant was not mentally disturbed..."
They may be partially correct - in a way. A person involved in Satanic worship may or may not give any clues via his demeanor or behaviour. Although, there are many different types/levels of such inverted worship. Some do give away their "belief" by modes of dress, speech, etc. These are usually the lower eshelon in the pecking order. This person may well be a victim of "obsession".
But, I would comment that this person, is probably one whose involvement is on a lower eshelon. The more dangerous ones do not make themselves visible, much less so obvious. Ones like this person do the dirty work for the higher ups.
Good tagline... but I thought it was "Vade retro, Satana. Numquam suade mihi vana."