I nominate PETA, long as we're engaging in paranoia. I wasn't engaging in paranoia so much as sarcastically bracing for the news media's fixation on the gun aspect (and by association, the right-wing aspect). At this point it could be terrorists, left-wingers, right-wingers, jilted lovers, crackpots, Al Gore, etc.
But I think it could be PETA. or Earth First. Anyone willing to kill loggers wouldn't have any trouble shooting a mom in front of her children. by the way, was she driving an SUV?
A PETA type is a possibility. The smiley face bomber was of that way of thinking.