JACKSONVILLE, Fla. -- A Jacksonville man who pleaded guilty to sharing child pornography online is heading to prison.

A federal judge sentenced Clifford Duncan to five years in federal prison for attempted transportation of child pornography. Duncan also has to register as a sex offender and give up his computer.

Investigators caught on to Duncan in April 2008. At that time, the Martin County Sheriff's office began investigating a file-sharing network that was distributing child pornography.

They discovered Duncan used the network, and traced him back to Jacksonville. With the help of officers in Jacksonville, they arrested Duncan in May of last year.

Investigators seized his computer and found numerous illegal videos. They said some of the videos he had portrayed "sadistic conduct involving children."