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Found skull uncovers child sex abuse material cache

Cheyenne man charged for sexual exploitation of a child

(Gregory Hirst, Oil City News)

CHEYENNE, Wyo. — John McMahon, 69, had his initial court appearance on June 12, facing charges of sexual exploitation of a minor for possession of child sex abuse materials. His bail was set at $10,000 cash. McMahon’s next court date is a preliminary hearing scheduled for June 20.

The investigation began on Sept. 23, 2023, when Officer Tretter responded to a call on East 24th Street. The reporting party had discovered a human skull inside a box while cleaning a residence for sale. Alongside the skull, floppy disks suspected to contain child sex abuse materials were found.

Detective Walker reported that the property owner was moving McMahon’s belongings, which were marked with an “A” for items he wanted back. Among these items were magazines, notes and eBay sales receipts for materials depicting young males in sexual positions. These items were logged into evidence by the Cheyenne Police Department.

On Sept. 28, an additional 47 floppy disks were turned over to Special Agent Seder from the Wyoming Division of Criminal Investigation. The disks had titles suggesting child sex abuse materials, including phrases like “minor site samples” and “hung little boys.” These disks were subsequently logged as evidence.

The case took a critical turn on Oct. 16, when the Wyoming DCI received 64 cybertips from the National Center for Missing and Exploited Children. These tips originated from Amazon Photos and included images uploaded on Sept. 6, suspected of depicting child sexual exploitation. The IP address linked to the uploads was traced to an establishment on Central Avenue, according to the affidavit of probable cause.

Further investigation revealed the Amazon Photos account associated with the cybertips belonged to JT McMahon, registered on East 24th Street. Detective Walker and SA Kniss reviewed additional evidence, including a computer and more floppy disks turned over by the property owner. A forensic search uncovered 612 visually unique files of suspected child sexual abuse material on McMahon’s computer and 264 unique files on the floppy disks.

The skull has been investigated by anthropologists at the University of Wyoming and is dated to be from the 1800s, according to Cheyenne Police Department Public Information Officer Alexandra Farkas. The CPD does not believe it is evidence of other criminal activity, and it has been turned over to the Laramie County Coroner’s Office.