Actually, I knew the part about serial killers usually being white and if you read books on profiling, etc., they will tell you this. To the best of my knowledge there has only been one black serial murderer identified and caught.
I think it's three: Williams in Atlanta, some guy in New Orleans and the DC area snipers(not white guys is a white van that moose insisted was involved)
You don't watch "The First 48" do you?
How do you define serial killer? Does it have to be someone who kills to satisfy some perverse, sick twist of his mind?
What about someone who killed for a gang initiation, in a robbery, to control a drug territory, because someone dissed him, because a woman cheated on him, to control a drug territory - who might have killed six times for various reasons? Is he a serial killer?
While the majority of serial killers are white/Eurams, if you'd watch the Discovery Channel, and maybe a few other cable channels featuring real crimes (Archives of the FBI, Real Detectives, etc.), you'd "discover" that there's been numerous serial killers of all ethnic groups... including Aframs and Hispams.