WICHITA, Kan. » Federal authorities investigated numerous death threats over the years against a late-term abortion provider who was eventually shot to death, including a 1999 letter that claimed a group of militant abortion opponents meeting in Las Vegas paid a woman $25,000 to kill him.

Nothing came of that investigation and several others into threats against Dr. George Tiller, who was gunned down at his Wichita church in May 2009 by anti-abortion activist Scott Roeder. The investigations were disclosed in 287 pages of documents released this week by the FBI under a Freedom of Information Act request by The Associated Press.

The documents released to the AP are heavily redacted and aren’t related to Tiller’s death. Nearly half of the pages in his FBI file remain secret, partly under rules that prohibit disclosure of grand jury proceedings.

Those documents mostly cover cases in which the U.S. attorney’s office declined to prosecute or cases in which federal investigators could not identify suspects. Nearly all were more than a decade old.

As one of the few doctors in the nation to provide late-term abortions, Tiller had long been a target of both peaceful and violent protests. He was shot in both arms in 1993 by activist Rachel "Shelley" Shannon, and his clinic was bombed in 1996. The clinic has been closed since his death.

Among the documents released by the FBI were investigators’ notes related to two letters written in 1999 by a woman who was later found to have mental problems. The woman wrote to her former husband in Arkansas City, telling him about a plot hatched in Las Vegas by a group calling itself the All Prayer Warriors. Investigators interviewed the woman, who said she had made up the group’s name and never actually met with anyone when she was in Las Vegas about harming Tiller.

The U.S. attorney’s office in Wichita, after reviewing the case, declined to prosecute her, the documents show. The FBI agent in charge of the case agreed with that decision.

Nonetheless, Tiller’s lawyer requested that the doctor be provided with protection by the U.S. Marshals Service during July 1999 the month when the woman’s letter stated the doctor was to be assassinated. The documents do not indicate whether the doctor got the requested protection at that time, although the U.S. Marshals Service had at times provided him with such protection.

Tiller family attorney Lee Thompson declined to comment Monday on the FBI documents or authorities’ handling of death threats against his slain client.

The FBI also investigated claims in November 1996 that an anti-abortion activist living in Milton told an inmate at a women’s prison in Topeka that he planned to kill Tiller. It’s unclear who the inmate or the visitor was because the FBI blacked out all names in the documents.

However, Shannon was in that prison at that time. And the inmate told the FBI the same activist visited her at the Sedgwick County Jail in 1993 the same time Shannon was being held there for wounding Tiller.

Jay Greeno, the attorney who represented Shannon at her trial, said he was unaware of any FBI visits to Shannon while she was imprisoned in Topeka. Shannon is currently serving time in a federal prison in Minnesota after being convicted in a series of abortion clinic arsons and bombings.

Roeder testified during his murder trial that he visited Shannon when she was imprisoned in Topeka. However, his ex-wife, Lindsey Roeder, said she did not believe her ex-husband ever lived in Milton. Roeder is serving a life prison sentence.

The female inmate told FBI agents that the activist who visited her did not discuss a timetable or plan. She also said she didn’t think the man was serious. The activist denied to FBI agents that he had considered killing Tiller, though he refused to undergo a polygraph.

The FBI closed its investigation after federal prosecutors said they considered "the matter hearsay, without foundation, and lacking prosecutive merit."

Other death threats the FBI investigated included that of a woman with a history of threatening Tiller who told a nurse at a Wichita hospital in 2000 that she planned "to finish the job" on the doctor. The U.S. attorney’s office told her defense attorney it would prosecute the woman for her all of her threats if she made another one.

Federal prosecutors also declined to prosecute a Navy veteran who walked into a Topeka veterans’ hospital in 1999 and threatened to kill Tiller. He later told investigators he was not serious but made the threat in an effort to get treatment. In declining to charge him, the U.S. attorney’s office said he was mentally unstable at the time.

Tiller’s FBI file shows several other investigations in which no suspects were identified, such as a 1994 incident in which a grenade was left in a paper sack outside Tiller’s clinic, a suspicious package made to look like a bomb in 1998 and anthrax hoax letters sent in 2002.