The man identified by police in Kansas as the suspect in the killing in a Wichita church of a prominent abortion doctor had a history of mental illness, according to members of his family, and may have been intent on taking drastic action in support of his right-to-life views for many years.
The authorities confirmed they were holding 51-year-old Scott Roeder after stopping his car about 170 miles from the church were George Tiller was gunned down on Sunday as he handed out church bulletins at the start of the morning service. He is likely to be charged with murder and aggravated assault, officials said.
Meanwhile, the US Attorney General, Eric Holder, said that federal marshals were being dispatched to family planning clinics across the country to reinforce protection for abortion providers in the wake of the killing.
Mr Tiller had long been the focus of the anti-abortion movement because he was one of only a few physicians offering late-term abortions where the foetus may be 20 weeks into gestation or further. In the Eighties, his Wichita clinic was firebombed by protesters and 16 years ago he was wounded in both arms in a shooting.
The order to beef up protection at clinics was aimed at those several other doctors offering late-term terminations in different states. One such doctor was yesterday at work as usual at his clinic in Boulder, Colorado, where US marshals were present.
While the leading anti-abortion group, Operation Rescue, issued a statement condemning the killing, its leader, Randall Terry, said its activities opposing abortion would continue. While he reiterated that he considered the murder to be wrong, he added that Mr Tiller was a "mass murderer and horrifically, he reaped what he sowed".
In a statement made to the Topeka Capital-Journal newspaper in Kansas, David Roeder, the brother of the suspect said he had "suffered from mental illness at various times of his life". It went on: "We are shocked, horrified and filled with sadness at the death of Dr Tiller and the circumstances surrounding it that may have involved Scott Roeder. We know Scott as a kind and loving son, brother and father who suffered from mental illness at various times in his life. However, none of us ever saw Scott as a person capable of or willing to take another person's life."
Others came forward to recall some of what Mr Roeder had purportedly publicly advocated in the past.
"I know that he believed in justifiable homicide," Regina Dinwiddie, a well-known abortion opponent and protester told the Kansas City Star. "I know he strongly believed that abortion was murder and that you ought to defend... both born and unborn."
A man with the name Scott Roeder has also posted messages on the websites of anti-abortion organisations. One such statement was posted in 2007 on the Operation Rescue site. "Sometime soon," it asked, "would it be feasible to organise as many people as possible to attend Tiller's 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?"
Clarence Roeder, who identified himself as the suspect's uncle, also issued a statement. "This is a tragedy for the Tiller family and we feel so badly about that, that Scott would murder the doctor in the Lutheran church."