Certainly, no one familiar with the movement was surprised when the Earth Liberation Front (ELF) claimed responsibility for the $700,000 arson. Like the attack, the press release was standard operating procedure for the ELF, a loose-knit group of individual activists and tiny cells that has claimed responsibility for millions of dollars in damage.

But this communiqué was anything but routine. While the ELF and its sister group, the Animal Liberation Front (ALF), have been tagged by the as America's top "domestic terrorism" threat, their activists have always insisted that the "terrorist" label is wrong.

The two groups openly promote economic sabotage and other "direct actions" — they're blamed for more than million in property damage since — but have consistently cautioned followers to steer clear of harming people. The 's manual for new members requires them "to take all necessary precautions to ensure no one is physically injured."

It may be time to rewrite the manual. The Sept. 3 statement claiming the Pennsylvania attack made it clear that some of the ELF's operatives have decided to trade in property attacks for terror.

"[S]egments of this global revolutionary movement are no longer limiting their revolutionary potential by adhering to a flawed, inconsistent 'non-violence' ideology," the communiqué said.

"While innocent life will never be harmed in any action we undertake, where it is necessary, we will no longer hesitate to pick up the gun to implement justice [emphasis added]."

Lest this chilling message be misunderstood, the statement went on: "The diverse efforts of this revolutionary force cannot be contained, and will only continue to intensify as we are brought face to face with the oppressor in inevitable, violent confrontation. We will stand up and fight for our lives against this iniquitous civilization until its reign of TERROR is forced to an end — by any means necessary."

This dramatic ideological shift toward violence reflects, at least in part, the potent influence of a British-born group called Stop Huntingdon Animal Cruelty (SHAC). Since brought its openly terroristic approach to the United States in 1999, members have participated in its campaign of harassment against employees of companies who do business with Huntingdon Life Sciences, one of the world's largest animal-testing firms.