A former Denver preschool teacher pleaded guilty Thursday to distributing child pornography from a collection that prosecutors said was one of the largest in the U.S.

David Paul Moe, 46, of Denver was held without bail in U.S. District Court in Denver pending a sentencing hearing in September.

Two of the three counts in the indictment were dropped as part of a plea arrangement. Moe could have faced as long as 50 years in prison had he been convicted of all counts in a trial that was to have begun June 6.

Many details of the investigation remain unknown, because much of the case record is redacted, as is common in cases involving juvenile victims. But enough of it is available to make it clear that it could be one of the worst child pornography cases in U.S. history.

Moe taught and directed before- and after-school programs at Paddington Station Preschool in Denver for 18 years before he was arrested in a federal online sting operation July 24. For about 10 years, he was also downloading and distributing images and videos of child pornography, he admitted as part of the plea agreement.

In hearings leading up to the plea agreement, federal investigators testified that the extent of Moe's collection stunned them.

Prosecutors said investigators found 4,100 images of children on just one of hundreds of seized CDs. Along with six portable hard drives and two desktop computers, the pornographic material may have taken up half of the almost 6 terabytes of data seized from Moe's home, Homeland Security agents testified.

According to court documents, the images and videos showed very young girls fully or partly nude in sexually provocative poses.

Typical of the images, as cited in the original July criminal complaint, was one that "depicts minor female child approximately eight (8) years old. The female child is nude from the waist down wearing a pink and white shirt. The female child is lying on a bed with both legs spread towards the camera."

Moe was originally charged with three broad counts: knowingly distributing and attempting to distribute child pornography; attempting to receive child pornography; and owning a computer disk and other materials that contain images of child pornography.

Because of the deletions from the public records, it's impossible to know whether any of the children in the images were ever pupils of Moe's. But the case record reveals that Moe was accused of improperly touching a 3-year-old child at the school in 2001, an accusation that was never followed up on.

Moe also kept an 800-page, single-space journal of his daily interactions with more than 100 of his pupils.

In an order granting Moe bond last year, a judge wrote that none of the behavior described in the journal was illegal but that some of it was troubling, citing entries like "Had (redacted) by the hips, and she was fine by that" and "Gave her a kiss on the cheek, and no bad reaction. ... I love her so much."

The journal demonstrated "a strange and potentially disturbing preoccupation with Defendant's non-sexual interaction with those left in his care," U.S. Magistrate Judge Michael Hegarty wrote in the August order. But it "is also remarkable for demonstrating a lack of criminal intentions toward those children."

Moe was never freed because he refused to accept one of the bond conditions, an order that he be confined to his parents' home, the case record shows.

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In the wake of Moe's arrest, the Paddington school lost more than 20 percent of its more than 300 children, it said, and founder Pippi Hambidge resigned as director. School administrators ordered training for remaining staff, changed pupil pickup and delivery procedures and added cameras at all doors.

In a statement Thursday, the school stressed that "there remains no indication that the charges against Mr. Moe included any involvement (photographs or otherwise) with any Paddington students."

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