Maricopa County Sheriff's officials said 50-year-old James Robert Desilva is being held on suspicion of 10 counts of sexual exploitation of a minor.
"These files that detectives were able to obtain depicted 70 or more videos and pictures of children from the ages of 4-to-11 engaged in sexual acts," Deputy Joaquin Enriquez said.
The investigation into Desilva's alleged use of child pornography began in October of 2011 when detectives of the sheriff's office received a tip from Child Protective Services about an IP address that was sharing sexually explicit images of minors.
"Sherriff Joe Arpaio and his detectives realized how complex this case is -- adding to the fact that James is an IT specialist," Enriquez said.
The deputy said when the investigation began, Desilva had cooperated with detectives, but is currently refusing to give them his computer password.
"Desilva, who once applied for the Surprise Police Department and Glendale Police Department, admitted to sheriff's deputies that he downloaded videos of bestiality and videos of bomb making and terrorism-type videos which he has on his computer," Enriquez said.
Desilva was arrested Monday at his El Mirage home and taken into custody. He's being held on a $100,000 bond from a grand jury warrant.
It was unclear Monday night if he has a lawyer.
The Associated Press contributed to this report.