Wichita NBC affiliate KSHB-TV is reporting that the suspect being held in the assassination of Dr. George Tiller is a man named Scott Roeder. Posters in the forums at the DemocraticUnderground have identified at least one posting at Operation Rescue's website (currently down, link to Google cache here) that's written by a Scott Roeder and refers to Dr. Tiller.
There is also information that indicates that a suspected Freeman named Scott Roeder was arrested in Topeka in 1996 for parole violations related to his having bomb making materials in his car trunk. At that time, he was identified as being 38, which would make him 51 today. Another recent news report gives the current age of the suspect in Tiller's assassination as 51.
The information currently available strongly suggests that this Scott Roeder is exactly the kind of radical right-wing extremist that was discussed in a recent Homeland Security report - you remember that report, right? It's the one that various semi-mainstream conservatives got all self-righteously irate over a couple of months ago.
Update (semi-): I've got some additional thoughts on the matter, including the question of how much (if any) responsibility the broader anti-abortion movement shares with the gunman, here.
I also added a link to Tarc's original thread at DU that had the link to the Google Cache for the Op Rescue post. I should have had that link up before now - sorry I missed it.