From Western Standard:
According to news reports, police have detained a suspect in Dr. Tiller's murder. The suspect, Scott Roeder has connections to Operation Rescue, as documented here (yes, normally I would have qualms about the source, but everything is well supported with supplementary links.)
It appears that Roeder is also a tax protestor, linked to the Montana Freemen, a group that -- if not exactly libertarian -- espouses libertarian-like views about individual sovereignty and the illegitimacy of government.
FWIW, wiki describes the Freemen as a "Christian Patriot" group. Quite a few of its members are doing time.
Quite a "nuanced" discussion over at the Western Standard. Of course murder is wrong, and yada yada yada...
Meanwhile this report is looking quite prescient.