FREMONT — Prosecutors have charged a man with possessing child pornography after his ex-girlfriend told police she found a digital “pedophile handbook” on his computer, court records show.

Kaden Peper, 22, now faces a single felony charge of possession or control of child pornography. It all started when Peper allegedly left his computer in his ex-girlfriend’s car, then called to inform her of the mistake, authorities said.

The woman discovered a file labeled “pedophile handbook,” described by police as a multi-page document describing child sexual abuse and how to be a pedophile. There were two other folders labeled “pics” and “vids” but she wisely didn’t open those, police say.

The woman brought the computer to the Fremont Police Department. Investigators in turn arranged a pretext call between her and Peper, in which he allegedly stated he was “attracted to teenagers not toddlers,” and that he even sought a relationship with his ex “because she was petite and looked young,” an investigator wrote in court filings.

Police allege, though, that Peper’s computer contained videos depicting prepubescent children being sexually abused.

Peper pleaded not guilty at a Thursday morning court appearance. He is out of custody, with a court order instructing him to obey the law and not look at any child pornography, a minute order from the hearing says.