WASHINGTON (CN) - With the self-proclaimed Islamic State promising more carnage abroad as the Syrian conflict rages into its fifth year, the United States is grappling to understand the extent of homegrown radicalism here and how to address it.
Seamus Hughes, the director of George Washington University's Program on Extremism, says the most important thing for Americans to understand is that there is no typical ISIL recruit.
"They can be old, young, rich, poor, black or white," said Hughes, who co-authored a new report that studies the motivations of 80 suspected Islamic State sympathizers arrested in the United States since March 2014.
The December 2015 report finds that only a handful of these individuals reached midlevel leadership positions within the terror group commonly abbreviated as ISIL or ISIS.
Level of support for the group also varies widely among arrestees, Hughes said, noting that suspects range "from a 17-year-old tweeting in his parents' basement, to hardened terrorists."
Profiling someone who might become radicalized is a "highly individualized" process, where ideological and personal motivations are deeply intertwined, Hughes added.
Some commonalities do appear in the study, however, which found that 88 percent of suspects are male and that their average age is 26.
Most were arrested for "intent to do harm overseas or for providing material support - namely personnel and funds - to fighters in Syria and Iraq," the report says. About 30 percent were involved in plans for domestic attacks, and 40 percent were converts to Islam.
The FBI counts more than 900 active investigations of alleged ISIL sympathizers in all 50 states, and says 250 Americans have traveled or attempted to travel to Syria and Iraq to join the group.
That's more than in any single year since the terrorist attacks of Sept. 11, 2001.
Factors that had a magnetic draw for these American Muslims included feelings of disenfranchisement, a search for personal fulfillment and belonging, and a quest for a sense of identity, community, love, and counterculture, according to the report.
Some were also outraged by the horrific violence of Syrian President Bashar al-Assad's regime, and the perceived indifference and inaction of the international community while the regime slaughtered civilians.
"Pictures and videos capturing the aftermath of civilian massacres perpetrated by the regime, displayed widely in both social and mainstream media, rocked the consciences of many - from those with an existing strong Sunni identity to those who were not Muslim - and led some to take the first steps to militancy," the report says.
The report found many cases where an individual's link to the group was limited to online declarations of support. More than half of the arrests involved a sting operation or an informant - a controversial phenomenon that many have condemned as entrapment of individuals who would not have acted on their own.
Hughes distinguished the United States from other countries by its lack of outreach to help radicalized individuals before they end up in the criminal-justice system.
"If you have a 16-year-old and he's watching ISIS videos or talking about traveling abroad, who do you call?" Hughes asked. "You don't want to risk him being arrested. So you're stuck in an untenable position."