The Justice Department said the Santa Rosa-born man, Elvin Williams, was getting ready to board a flight on Friday when he was stopped by federal agents.
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FBI officials tell ABC7 News, this wasn't the first time the bureau was alerted about the man's behavior.
A 36-page criminal complaint shows texts messages between Williams and men he didn't know were FBI sources. In screenshots, one source asked if Williams had a problem with killing.
Using the name Ali Ar-Rusi, Williams wrote back, "No I do not. Not in the slightest bit."
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"He was consuming these videos and propaganda for hours at a time," Steve Bernd with the FBI explained. "It's hard to detect. That's why we need people to tell us if they think something is awry. Let us at least have the chance to take a look at it."
Bernd is a Public Affairs Specialist with the FBI's Seattle office.
He said the bureau was first tipped off to Williams back in 2017 by his own mother and high school administrators.
"He had come to our attention in 2017, after some disturbing remarks he made at his high school," Bernd told ABC7 News. "But we have not been actively investigating him since 2017."
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"He was brought to our attention after some comments he made regarding activities at the Ariana Grande shooting in Manchester, England," he continued. "But more recently, in November of 2020, he was brought to our attention as someone that was potentially dangerous by members of his mosque."
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Bernd said people at the Seattle-area mosque were attempting to "steer him on the correct path."
"They were working hard to try to get him on the on the straight and narrow," he said. "They had provided him a phone and a laptop to help with his job search. And once they got the phone back and were able to search through that, and saw some very disturbing propaganda videos that he had downloaded, they had brought it to our attention."
Court documents show Williams was aware. A screenshot showed Williams wrote, "I got reported to the FBI again. I need to hurry up and leave already."
He was arrested last Friday at Sea-Tac Airport. Investigators said he was only moments from boarding a flight to Egypt, flying through Amsterdam and Paris.
"Just buying the plane ticket wasn't enough," Special Agent Donald Voiret explained. "We wanted to be able to see him show up at the airport, crossover, where he was actually in the jetway boarding the plane when he was arrested."
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"So he could never say, 'You know what, I changed my mind' or 'I was not going forward with my intent of fighting overseas,'" Voiret continued.
Messages released by the FBI show Williams trying to convince an FBI informant to drive a semi-truck through Seattle's Gay Pride Parade as well.
"He was determined to join ISIS and got a job for the sole purpose of earning money to buy a plane ticket and supplies he would need to go to the Middle East and fight," Bernd added.
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"This has been a great success, working with our partners, and with other federal partners, state partners, locals as well the community," Bernd told ABC7 News. "If it hadn't been for the people that became concerned at his mosque, and others that alerted us to where they thought he was going, this might not have ended the way it did."
From the moment Williams was reported by people at his mosque, to his arrest last Friday, Bernd said the timeline made perfect sense.
"That is right in the timeframe that you see someone that is radicalized, mobilize to action," he said. "It's in that six-month timeframe."
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Bernd shared, "If you're concerned that a loved one, or a friend, or an acquaintance may be going down a path such as Mr. Williams, contact local law enforcement. Contact your local FBI office, just let us know so we can take a look at it."
The FBI said Williams is charged with attempting to provide material support to a foreign terrorist organization.
"And the 'material support' is actually his person," Bernd clarified. "He is offering his person to fight for ISIS."
If convicted, Williams could face up to 20 years in prison.