A Southern California man was arrested on Friday and accused of possessing what prosecutors called one of the largest child pornography collections ever recovered.

Michael Peterson, a 58-year-old pipefitter, was taken into custody at his home in Ontario, about 35 miles east of Los Angeles, on charges of possessing, receiving and distributing child pornography.

Acting on a search warrant, federal agents had raided Peterson's home in July and seized computers and several hard drives with 500,000 images and 7,500 videos of suspected child pornography, U.S. District Attorney's spokesman Thom Mrozek said.

It's not uncommon for us to see collections of thousands and sometimes tens of thousands of images, but in this case we have over half a million images being stored on numerous devices, Mrozek said.

It may in fact be the largest child pornography collection ever discovered in the United States, he said.

The children in the images and videos range in age from 18 months to 17 years old and were either nude or involved in sexually explicit acts, the criminal complaint filed against Peterson said.

When Immigration and Customs Enforcement (ICE) agents raided Peterson's home, they found two laptops on a table with a half-eaten bowl of cereal, one of them actively downloading child porn through a peer-to-peer network, the criminal complaint said.

Virginia Kice, a spokeswoman for ICE, said that episode demonstrated how much time Peterson devoted to collecting child pornography online.

It's someone who's a prolific user, and it's frankly a frightening thought, Kice said.

Authorities found Peterson after an undercover federal agent downloaded child pornography from him through a peer-to-peer sharing website, and tracked down the Internet Protocol number on Peterson's computer, the complaint said.

ICE agents led the investigation that nabbed Peterson because the agency is charged with investigating cases of child pornography, Kice said. U.S. authorities have not accused Peterson of producing child pornography himself.

He faces a maximum sentence of 50 years in prison if convicted. An attorney for Peterson could not be reached for comment.

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