"I have directed the United States Marshals Service to offer protection to other appropriate people and facilities around the nation," Holder said in a statement released late today by the Justice Department. "The Department of Justice will work to bring the perpetrator of this crime to justice. As a precautionary measure, we will also take appropriate steps to help prevent any related acts of violence from occurring."
Tiller's attorneys gave The Associated Press a statement on behalf of his wife, four children and 10 grandchildren.
"Today's event is an unspeakable tragedy for all of us and for George's friends and patients," the statement said. This is particularly heart-wrenching because George was shot down in his house of worship, a place of peace.
"George dedicated his life to providing women with high-quality heath care despite frequent threats and violence," the statement added."
Lindsey Roeder, the suspect's ex-wife, said she came home from church today to find FBI and ATF agents going through her house in Overland Park, Kan., which is about three hours outside Wichita.
When they said they were there investigating the killing of a doctor who provided abortions, she felt instantly that her ex-husband was likely involved.
Lindsey Roeder said it was Scott Roeder's strong anti-abortion views that led to the couple's 1996 divorce. She said her ex-husband never kept quiet about his views on abortion.
"My family does not condone or support what Scott has done. This event is a tragic and senseless one and our thoughts and prayers are with the congregation and the doctor's family," Lindsey Roeder said.
She said her former husband was a member of the Freemen in Missouri and has a criminal history that includes an 1996 arrest for various parole violations and having bomb making materials. She said he did do some time on charges related to those issues, but was released on a technicality.
She said that Friday night Scott Roeder was adamant about seeing his 22-year-old son, Nick, who she claimed has tried to avoid his father and only saw him about once every six weeks growing up.
"My son is only related to his father by blood and does not believe in any of the same views his father does," she said.
The two did meet Friday night, though, she said, and she believes the meeting was meant as a goodbye from father to son.
For decades, Tiller has been a target of anti-abortion violence. In 1985, his clinic was bombed, and in 1993, he was shot in both arms outside the clinic by Rachelle Shannon of Grants Pass, Ore. He testified at Shannon's trial.
Tiller said he initially thought rubber bullets had been fired, according to ABC News Radio.
"I looked down at the floor and there's blood all over the place and there's glass all over the place. And I figured I'd been shot," he said in 1994.
After the 1993 shooting, Tiller immediately returned to work. The controvserial abortion doctor often wore a bullet-proof vest and drove an armored car, ABC News' Stephanie Sy reported. He was guarded by federal marshals for three years.
"I have a right to go to work," he said in 1991. "What I'm doing is legal. What I'm doing is moral, ethical, and you won't run me out of town."
Tiller is believed to be the first abortion doctor to be killed since Barnett Slepian was assasinated in Amherst, N.Y. in 1998.