I don't know, Reiser is not a serial...

I think there's a personality anti-correlation that keeps this mostly exclusive.

Serial killers tend to be more outgoing and active (to a troubling degree), whereas coders who create their own languages tend to be indoors types who don't mind sitting in one place for long periods.

I mean there are plenty of psychologies that could make for someone who does both, but it would seem to reduce the odds a lot.