Material support to an act of terrorism.
Edit - from the search warrant application: "will be found evidence of violations of federal law, namely, intentional obstruction, by force or threat of force of persons in the free exercise of religious belief, resulting in death, in violation of 1 S U.S.C. § 247(a)(2), willfully causing bodily injury to persons through the use of a firearm because of the actual or perceived religion of said persons, resulting in death, in violation of 1 S U.S.C. § 249(a)(l), and damage to religious property, in violation of lS U.S.C. § 25 247(a)(l )"
Edit 2: Lots of legal eagles on HN today that are upset at the word "material." Sorry? If you read the full search warrant it sounds like he torched a synagogue, and was encouraged to follow up with a shooting.