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PHILADELPHIA (CBS/AP) — A Pennsylvania man has been sentenced to 100 years in prison for what authorities say was the largest collection of child pornography state law enforcement officials have seen.

Lawrence Jamieson was sentenced Monday in federal court after pleading guilty in September 2017 to sex crimes and child pornography charges.

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Authorities say the 59-year-old Jamieson had more than 14.4 million images and videos of children and infants being sexually abused.

Jamieson’s stash of images collected over 15 years was discovered when he was arrested on charges he and an accomplice tried to manipulate an underage girl with learning disabilities into performing sex acts on both men. Prosecutors say they filmed and distributed footage of those acts.

Jamieson was arrested in August 2016 after Willistown police received a report about child sexual abuse.

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Prosecutors called Jamieson’s collection “some of the most demented images imaginable.”

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)