Since 911, no Americans have been killed on U.S. soil by Islamist extremists. But at least six American law enforcement officers have been killed by home-grown terrorist groups. In the words of one extremist apprehended after slaying a police officer in California, his action was intended "to bring attention to, and halt, the police-state tactics that have been used throughout our country." Among the perpetrators have been members of the self-proclaimed Michigan Militia, the Aryan Brotherhood, the National Alliance, and a "Christian Identity" group.
In addition to these killings, domestic extremists have been involved in numerous instances of attacks on individuals or institutions, ranging from Hispanic citizens to synagogues. Just since the beginning of October, police in Idaho apprehended an extremist with a number of improvised bombs, a woman in Michigan was stabbed by neo-Nazis for "distrespect" to their regalia, while in Sacramento three members of the "Earth Liberation Front" pleaded guilty to attempted arson in connection with an attempt last December to burn down two homes under construction.
It is estimated that there are over 800 extremist groups in the United States. Most of them specialize in racial or religious hatred, though a fair proportion have political agendas, ranging from neo-Confederates to radical anarchists, plus some others such as animal rights radicals or eco terrorists.
Although domestic terrorists don't get the press coverage accorded to the foreign sort, they do get considerable attention from both official and non-governmental organizations. The FBI, for example, keeps tabs on any group likely to commit criminal acts, regardless of agenda. For example, it recently reported to Congress on "Investigating and Preventing Animal Rights Extremism," and has been probing possible links between Aryan Nations neo-Nazis and Islamist terrorists. The two most prominent non-governmental groups that monitor domestic extremism are the Southern Poverty Law Center, which focuses on racist and right-wing groups, and the Anti-Defamation League of B'nai Brith, which concentrates on groups with an anti-Semitic program .