Aaron Guzman, 43, was taken into custody in Clovis.
Investigators say they found pictures and video of children as young as five years old inside Guzman's apartment.
Detectives believe Guzman was collecting child pornography online for the past 15 years.
His arrest is the result of a two-week investigation involving the sheriff's office, Clovis Police and the Homeland Security Department.
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