Federal investigators say the suspect came under their radar when a video of him engaging in sexually explicit activities with a young boy was reported to the National Center for Missing and Exploited Children in November 2012.
The suspect is described as a white male believed to be in his 30's or 40's with a receding hairline and wire-frame glasses.
There are no details linking the suspect to a particular area, but investigators say they believe he may be a U.S. citizen because he spoke English during the video.
Anyone with information on John Doe 28 should submit a tip online or call the the toll-free F.B.I. tips line at 1-800-CALL-FBI.