Paul Duffy, an attorney for the Prenda Law, died on Monday, a Cook County Medical Examiner spokesperson said, adding that the cause of death is still pending and could take up to three months to confirm. He was 55.

Prenda made millions by suing Internet users for allegedly downloading porn illegally, banking on the fact that most of the people receiving its lawsuit threats would choose to settle rather than endure the cost and embarrassment of a lawsuit—even if they did nothing wrong. Duffy was considered a principal for Prenda Law, but he also worked closely with John Steele and Paul Hansemeier, who were affiliated with Prenda's litigation.

As Prenda's business began to unravel amid accusations of identity theft and signature forgery, the firm began to pursue defamation lawsuits for online criticism. US District Judge Otis Wright had Prenda's practice referred to the Internal Revenue Service's criminal investigation unit and in August 2014, the US Court of Appeals for the Seventh Circuit upheld judicial sanctions against Duffy, Steele, and Hansmeier for engaging in “abusive litigation” and failing to pay attorney's fees to defendant Anthony Smith in a porn-downloading lawsuit.

In June, US District Judge David Herndon ruled that Steele and Duffy had "engaged in unreasonable, willful obstruction of discovery in bad faith" in its case against Smith. Herndon ordered Duffy and Steele to pay for the defense's discovery costs.

Correction: The story originally indicated that Duffy was ordered to pay discovery costs in a defamation suit. Those costs actually pertained to the suit against Anthony Smith.