Neighbors of Sean Andrew Duncan were shocked to see the FBI raiding his Sterling, Virginia town home on Friday night, taking away boxes of evidence of his alleged ties to ISIS, according to an FBI affidavit obtained by WJLA.

The moment agents showed up at Duncan’s home on Friday, “he ran out the back door, barefoot, and with something in his hand,” the affidavit alleges. The man then threw a plastic baggie, which was found to contain “a memory chip stored within a thumb drive that had been snapped into pieces, and placed in a liquid substance that produced frothy white bubbles.”

According to the affidavit, Duncan had recently tried to visit Turkey with his wife, but the country deported him back to the United States. Earlier in December, a detained ISIS recruiter revealed a handwritten list of names and phone numbers, which contained Duncan’s information.

And a previous search of Duncan’s cell phone over the summer uncovered “numerous internet searches for ISIS-related materials,” including information on ISIS attacks, weapons, body armor, surveillance and defense tactics, and paintball venues.

In July, an unnamed co-conspirator told the FBI that Duncan had connected with her on social media and said he was interested in joining ISIS and conducting a terrorist attack in the United States. He also asked her to travel to Syria with him and his wife, but she declined, the document says.

The FBI conducted an undercover sting in August, during which time an agent posing as a co-conspirator identified an encrypted messaging account associated with Duncan. The agent was able to ask Duncan if he had any connections in Syria, the affidavit alleges, and Duncan answered, “No a couple have been marytred (sic).”

According to court documents, Sean Duncan moved from Pittsburgh to the D.C. area in June. Around that same time, Allegheny County detectives were investigating the death of Duncan’s infant child. Allegheny County Director of Communications Amie Downs released the following statement Sunday:

“County Police were investigating the death of Sean Andrew Duncan’s 4-month-old son, Muhammad, which occurred on June 6, 2017.

The incident occurred in Aspinwall, although the child died at Children’s Hospital ER. He was four months old. The cause of death was determined to be sudden unexplained infant death and the manner of death could not be determined.

In the course of that investigation, the FBI contacted the ACPD for cooperation in a separate investigation, which they provided.”

Federal investigators first became aware of Duncan’s activities in February 2016 after a relative reported to the FBI that he had allegedly converted to Islam and had possibly become radicalized, according to WTAE Pittsburgh.