An Icelandic man who played a major role in the FBI’s case against WikiLeaks founder Julian Assange has been arrested in Iceland after authorities say he embarked on a brazen crime spree. Assange supporters say the arrest of Sigurdur Thordarson, reported by the Icelandic newspaper Stundin, deals yet another blow to his credibility after he gave an interview over the summer saying he had lied in his testimony about Assange to U.S. federal investigators. Thordarson, a convicted criminal with a long rap sheet that includes convictions for sexual abuse of minors, was sent back to the country’s highest security prison on Sept. 24, according to Stundin. Sources cited in the report say authorities made the decision to throw him back behind bars after he racked up several new allegations of financial fraud, including one in which he allegedly forged his lawyer’s signature to inflate assets. Deemed a “sociopath” in a court-ordered psychological evaluation, Thordarson is a former WikiLeaks volunteer who said he became a paid informant for the FBI within the group.