-- Just days before the fifteenth anniversary of the Sept. 11, 2001 attacks, federal authorities have arrested a Kentucky woman who allegedly advocated online for terrorist attacks in the U.S. and promoted ISIS propaganda through her social media accounts, according to sources familiar with the matter.
The woman, identified as 55-year-old Marie A. Castelli, allegedly lied to authorities when confronted about her activities, sources told ABC News. According to jail records, her 56th birthday is on Sunday, the same day as the anniversary of the worst terrorist attack on U.S. soil.
The FBI arrested Castelli Thursday.
Castelli has been charged with knowingly transmitting threats online, and with lying to the FBI when agents confronted her about her activities.
Castelli appeared before a federal judge today for an arraignment, and the judge ordered that she be detained pending any further court proceedings.
"There is no current threat to public safety related to this arrest, and it is not related to the upcoming anniversary of the terrorist attacks of September 11, 2001," the FBI said in a statement.
According to the indictment filed in the case, in October 2015 she posted messages with the names and addresses of three unidentified "victims," and "stated that others should locate execute" one of them. The indictment does not mention ISIS by name.
An arrest usually indicates charges have been filed in some form, but it's unclear when or how charges have been filed in this case. Defendants in similar cases are often charged -- at least initially -- with the lesser offense of lying to federal authorities during the course of an investigation.
In an online forum, a woman from Maysville, Kentucky, dubbed "Jihad Marie Antoinette Castelli" said she is a Muslim "without a country that accept me for who I am," and she said she'd "love to meet face to face Sheikh Osama" and meet his family.
According to the Ledger Independent newspaper, Castelli is originally from New Jersey and then lived in Egypt for about 13 years after going through a difficult divorce.
In a LinkedIn profile cited by the Ledger Independent, Castelli says she lost many of her possessions during the divorce and gained a "hatred of the U.S. justice system and courts and lawyers."
Last December, a woman called Maysville police to express concern that Castelli was taking pictures of herself in front of a local courthouse, the police chief confirmed to ABC News.
Earlier this week, the heads of FBI offices across the country took part in a classified briefing with the Department of Homeland Security (DHS), state-level intelligence fusion centers and other local law enforcement to discuss "vigilance during the upcoming anniversary of 9/11," as the DHS chief of intelligence and analysis, Gen. Frank Taylor, put it.
However, the anniversary on Sunday is "not implicated in any way" as a reason for moving forward in the Kentucky woman’s case, one source said.
Nevertheless, Castelli's case highlights the types of threats facing Americans in the post-9/11 era and her case is a unique one.
By a margin of roughly 5 to 1, ISIS-related arrests tend to involve male suspects, according an ABC News review of cases.
In addition, the vast majority of ISIS-related suspects are under age 30, with a third of them under 21, according to Justice Department officials.
In all, over the past three years, more than 100 Americans have been charged with trying to join ISIS or are suspected of supporting the group in some other way.
"It was very important to do these disruptions, and I have no doubt that lives were saved because we did these cases," the head of the Justice Department’s National Security Division, John Carlin, told the Intelligence & National Security Summit in Washington, D.C., on Wednesday.
Speaking with Carlin on Wednesday, Deputy Director Andrew McCabe, the FBI’s second-in-command, warned that "crowd-sourced terrorism" is reaching "those folks who are maybe mentally unstable to begin with" or who are otherwise "marginalized."
"We’ve seen those folks discover [ISIS], become radicalized and then move to mobilization in incredibly short timelines," McCabe said. "That puts a lot of pressure on us."
Two weeks ago, the FBI and Department of Homeland Security issued a bulletin to law enforcement across the country, warning them that self-radicalized terrorists inside the United States are "focusing more on civilian targets."
ABC News' Audrey Taylor contributed to this report.