JACKSONVILLE, Fla. -

A 23-year-old St. Johns County man pleaded guilty Wednesday to receiving child pornography over the Internet.

Christopher O'Brien II faces five to 20 years in federal prison and a potential life term of supervision. A sentencing date has not yet been set.

According to court documents, an agent with the Florida Department of Law Enforcement in Jacksonville began an undercover investigation to identify people in that area who had access to and/or were trading images and videos depicting child pornography over the Internet.

The agent determined that a host computer in the area was hosting images of child pornography using a particular peer-to-peer file sharing program. The agent made successful connections to the host computer and successfully downloaded several video files depicting child pornography directly from the host computer. The agent found that the subscriber information traced back to O'Brien's home in St. Johns County.

On Feb. 26, 2013, FBI agents and other officers executed a search warrant at O'Brien's home and seized, among other things, several computers and other items of electronic media. O'Brien was at the home and told the agents that he uses the same file sharing program as the one detected by the undercover agent.

He said he only downloads videos and believed that he had four or five videos of child pornography on his computer, which he repeatedly watched and saved. He added that the children depicted in his collection of child pornography ranged from 8 to 15 years old.

A subsequent analysis of O'Brien's computer revealed that it contained about 838 videos, at least 50 of which depicted minors engaged in sexually explicit conduct.