– Abortion clinics across the country were taking extra precautions Wednesday after the abortion opponents who shot Wichita, Kan., physician George Tiller in 1993 and committed clinic attacks in several states was released from prison.

Rachelle "Shelley" Shannon, the Oregon woman whose actions once triggered a federal investigation into the possible existence of a national conspiracy of terrorists opposing abortion, had been living in a halfway house in Portland, Ore., since May. She has spent 25 years in custody.

"We're extremely concerned," said Katherine Spillar, executive director of the Feminist Majority Foundation. "We're alerting providers, briefing them and making sure they have enough security precautions in place. "This is a woman who inspired three murders."

Shannon's release was confirmed Wednesday by the U.S. Bureau of Prisons. She will be on supervised release for three years, the bureau said.

"She's going on probation," said the Rev. Donald Spitz, an abortion foe who has remained in contact with Shannon. "I don't think she'll be doing anything violent," he said. "Of course, no one knows, but I'd be very surprised."

He said he had no details on Shannon's plans: "She'll probably be trying to get her own place to live and looking for a job."

Shannon, 62, was sentenced to 11 years in prison for shooting and wounding Tiller and 20 years for six firebombings and two acid attacks at abortion clinics in California, Oregon and Nevada.

The former assistant U.S. attorney who prosecuted Shannon said he also has concerns about her being released.

"She's completely unrehabilitated," said Stephen Peifer, the lead prosecutor on Shannon's federal case in Portland in 1995. "She has the same mentality and goals that she had when she was convicted. "She may do something violent herself but that's not as likely as her counseling and advising other people to do it. That's her track record."

That's why stringent conditions will be placed on her during her probation, he said. "The probation office is going to be very careful in terms of her associates and naming people that she specifically cannot associate with. I'm sure she'll have strict supervision. They were very concerned."

News of Shannon's release has clinic operators on edge. In addition to showing no remorse, Shannon has been visited in prison by activists who believe that killing abortion doctors is an act of justifiable homicide, they said.

Clinic supporters also noted that Tiller, a target of abortion protesters because he was one of a handful of doctors in the country who performed late-term abortions, was shot to death in 2009 by Scott Roeder, who had admired Shannon and visited her many times in prison.

Among Shannon's other prison visitors in recent years was Regina Dinwiddie, who made headlines in 1995 when a federal judge ordered her to stop using a bullhorn within 500 feet of any abortion clinic.

Another was Dave Leach, an activist from Des Moines, Iowa, and another advocate of the "justifiable homicide" position. Leach said he visited Shannon once a year when she was at the Waseca federal prison in Minnesota. He said concerns that she might commit violence again were "silly," then added, "Well, I guess anything's possible with human beings.

The Rev. Katherine H. Ragsdale, interim president and CEO of the National Abortion Federation, said she had doubts. "She's not only committed multiple acts of violence herself, but has encouraged violence in others."

Shannon once wrote to her daughter, "It was the most holy, most righteous thing I've ever done. I have no regrets."