Then there's this from the Northeast Intelligence Network:
According to sources speaking to the Northeast Intelligence Network on the condition of anonymity, McDonald is not believed to be the only person involved in this slaying - and might not have committed the murders himself.
While incarcerated in the federal system, he reportedly associated with a group of inmates who were actively involved in Islamic counseling - receiving radical fundamentalist Islamic literature during his incarceration. The prison source told Northeast Intelligence Network director Douglas Hagmann that there is indeed a religious component to the murders, although McDonald is not alone. Investigators from this agency are continuing the investigation to determine the veracity of those claims.
I don't have any independent confirmation of this, but I'll be looking into it.