The man arrested on suspicion of murdering Dr. George Tiller has been identified as Scott Roeder:

The gunman fled, but a 51-year-old suspect was detained some 170 miles away in suburban Kansas City three hours after the shooting, Wichita Deputy Police Chief Tom Stolz said.

Although Stolz refused to release the man’s name, Johnson County sheriff’s spokesman Tom Erickson identified the detained man as Scott Roeder. He has not been charged in the slaying and was expected to be taken to Wichita for questioning.

And Scott Roeder posted a creepy comment at the Operation Rescue website in 2007, in this topic about Dr. Tiller: Operation Rescue® » Pray in May to Stop Abortion, Wichita, KS, May 17-20, 2007:

Scott Roeder Says:
May 19th, 2007 at 4:34 pm

Bleass everyone for attending and praying in May to bring justice to Tiller and the closing of his death camp.

Sometime soon, would it be feasible to organize as many people as possible to attend Tillers church (inside, not just outside) to have much more of a presence and possibly ask questions of the Pastor, Deacons, Elders and members while there? Doesn’t seem like it would hurt anything but bring more attention to Tiller.

(Hat tip: MrPaulRevere.)

UPDATE at 5/31/09 5:34:22 pm:

Another comment from Roeder is posted at anti-abortion site ChargeTiller.com:

Scott Roeder
Mon September 03, 2007, 09:49:40

It seems as though what is happening in Kansas could be compared to the “lawlessness” which is spoken of in the Bible. Tiller is the concentration camp “Mengele” of our day and needs to be stopped before he and those who protect him bring judgement upon our nation.

UPDATE at 5/31/09 5:37:05 pm:

Authorities discovered a Post-It note in his car with the phone number of Operation Rescue:

KMBC-TV in Kansas City reported that the suspect had a post-it note with the phone number of anti-abortion group Operation Rescue in his car, however that group issued a statement this morning denouncing the shooting.

UPDATE at 5/31/09 6:20:48 pm:

An Anti-Defamation League “Militia Watchdog” report provides some more background information on Scott Roeder: Calendar of Conspiracy Volume 1 Number 3.

July 7, Kansas: Scott Roeder is sentenced to sixteen months in state prison for parole violations following a 1996 conviction for having bomb components in his car trunk. Roeder, a sovereign citizen and tax protester, violated his parole by not filing tax returns or providing his social security number to his employer.

More info on the Sovereign Citizen Movement:

The sovereign citizen movement is a network of American litigants who claim to be “sovereign citizens”; that is, people who claim to have certain rights under English common law and to be unaccountable to the federal government. The litigants advance this concept in opposition to “federal citizens” who, they believe, have unknowingly forfeited their rights by accepting some aspect of federal law.

This “sovereign citizen” concept originated in the Posse Comitatus movement as a teaching of Christian Identity minister William P. Gale. It has gone on to influence the tax protester movement, the Christian Patriot movement and the Redemption movement. Gale identified the Fourteenth Amendment to the United States Constitution as the act that converted sovereign citizens into federal citizens, but other commentators have identified other acts, including the Uniform Commercial Code,[2] the Emergency Banking Act,[2] the Zone Improvement Plan and the supposed suppression of the Titles of Nobility Amendment.

(Hat tip: Thanos.)