Deadly Puzzle: ISIS's American Supporters 'Defy Easy Analysis'

— -- Researchers examining the lives of more than 70 terrorism suspects collared by the FBI over the past year found no typical profile among these Americans beyond the allure of the spectacular savagery of the "Islamic State," according to a report released today.

The average age of those arrested and several killed in violent confrontations with law enforcement was 26 -- but some who became radicalized and enamored by ISIS were in their teens and some were pushing retirement age, the study by the Program on Extremism found.

"It is apparent that the U.S. is home to a small but active cadre of individuals infatuated with ISIS's ideology, some of whom have decided to mobilize in its furtherance," the report said.

The pool of Americans supporting ISIS is not only unprecedented in the number of terrorism arrests since the 9/11 attacks in 2001, but includes women, who account for 14 percent of the arrests in a startling new trend largely unseen in U.S. counter-terrorism.

"They find the solution to their problems, real or imagined, in ISIS," said the report's author, Lorenzo Vidino. "But it's not just kids fantasizing about joining ISIS. There are some very serious cases.”

Also over represented among those picked up by agents for plotting or moving toward acts of violence in the U.S. or abroad are Muslim converts, who made up 40 percent of the cases studied.

The ISIS "caliphate," which tries to appear as a legitimate state, is "emboldening individuals and groups" to travel or support the group inside the U.S. homeland, said LAPD chief of counter-terrorism Michael Downing at a discussion of the report in Washington.

Law enforcement's overriding concern is "about preventing the next attack," and have charged some suspects with offense lesser than terrorism-related offenses, such as lying to federal agents.

"U.S. prosecutors have gotten a bit creative with charges," said report co-author Seamus Hughes, a former Senate and National Counterterrorism Center official.

The study, "ISIS in America: From Retweets to Raqqa," was a painstaking undertaking by a team from the program at George Washington University's Center for Cyber and Homeland Security, who examined arrests in 21 states.

"The profiles of individuals involved in ISIS-related activities in the U.S. differ widely in race, age, social class, education and family background. Their motivations are equally diverse and defy easy analysis," the report said.

As has been well documented, social media plays a central role as bait to those Muslims who are lured in by the appeal of the so-called "caliphate" declared in June 2014 by ISIS leader Abu Bakr al-Baghdadi in Syria and Iraq.

The Program on Extremism identified at least 300 active Twitter supporters of ISIS who appear to be inside the U.S. But with over 900 active investigations in all 50 states, researchers said there are almost certainly more than 300 Americans enamored by ISIS and radicalized toward supporting the violence that defines the foreign terrorist group.

Former State Department counter-terrorism official Alberto Fernandez said ISIS lures in American supporters with propaganda that is more secular in tone than what Middle Easterners are exposed to.

"The material in Arabic is more religious. The material in English is less religious," Fernandez said.

ISIS operatives in Syria often identify sympathetic voices on Twitter and actively engage them publicly through tweets and then private direct messages, before switching to encrypted smartphone apps for often lengthy efforts to turn subjects toward joining ISIS overseas or committing acts of violence here in the homeland, the report says, echoing previous comments to ABC News from U.S. officials.

Disclaimer: This story's reporter, James Gordon Meek, is a senior fellow at GW's Center for Cyber and Homeland Security, which released the study.