U.S. News and World Report February 2013:

Of the more than 300 American deaths from political violence and mass shootings since 9/11, only 33 have come at the hands of Muslim-Americans, according to the Triangle Center on Terrorism and Homeland Security. The Muslim-American suspects or perpetrators in these or other attempted attacks fit no demographic profile—only 51 of more than 200 are of Arabic ethnicity. In 2012, all but one of the nine Muslim-American terrorism plots uncovered were halted in early stages. That one, an attempted bombing of a Social Security office in Arizona, caused no casualties.