Chicago ? A former Roman Catholic priest pleaded guilty Thursday to possession of three computer discs and hundreds of pages of images showing naked boys engaged in sexual acts and sadomasochistic activity.

Vincent McCaffrey, 50, resigned from the priesthood in 1992. He later worked at a home furnishings store, managed a service station and sold insurance.

Authorities said some of the pornography which included images of boys as young as 6 beaten, bound and gagged, and locked in cages was found hidden under McCaffrey’s mattress.

Assistant U.S. Atty. Markus T. Funk told U.S. District Judge John Darrah that McCaffrey had “molested” someone while he was a priest. But Darrah cut him off and kept the hearing focused on the child pornography charges.

Information concerning McCaffrey when he was a priest is under court seal. But much of it could come out during the sentencing hearing scheduled to begin Dec. 9.

McCaffrey could be sentenced to as many as 20 years in federal prison and fined $500,000 if the judge agreed with federal prosecutors on all the points they say make the former priest’s crimes unusually serious.