Story highlights Michael Kadar was charged in April with making threatening phone calls to Jewish centers

Kadar has not been extradited to the US

(CNN) Federal authorities believe the 18-year-old man accused of making more than 100 threats to Jewish institutions earlier this year was paid by someone to make some of those threats, recently unsealed court documents reveal.

The man advertised his bomb threat "services" through a major so-called "Dark Web" marketplace recently shutdown by the Justice Department, according to court records.

Michael Kadar, a dual American-Israeli citizen, was arrested in March and later charged for his alleged involvement in the wave of bomb and active shooter threats that rattled Jewish community centers, schools and other institutions across the United States and abroad.

Federal authorities said in April that their investigation was ongoing, and unsealed court records -- first noted on Twitter by Seamus Hughes, deputy director of the Program on Extremism at George Washington University -- now claim that Kadar was running an online threat-for-hire service and show prosecutors may try to pursue criminal charges against one of his buyers.

"That ongoing investigation has identified a suspect believed to have ordered and paid for at least [sic] of the bomb threats made by Kadar," federal prosecutors explained in one court filing. "The FBI and local authorities in California intend to pursue criminal charges against the suspect."

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