When a parole officer knocked on Joseph Naso 's door in April 2010, he thought he was conducting a routine probation check.

Instead, he walked into the home of a serial killer .

When Naso—who was on probation after a petty theft conviction for shoplifting women's lingerie—objected to a search of his Reno, Nev., residence, the cop called for backup.

As detailed by multiple investigators in the new Oxygen docuseries Death Row Confidential: Secrets of a Serial Killer , premiering Sept. 13, officers discovered thousands of photographs of women—some nude, some in nylons and garters, and many with their wrists and feet bound.

And, Nevada Dept. of Public Safety Major Crimes Unit Sg. Rick Brown said in the series, the pictures appeared to be of "deceased women."

Also found inside th

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