The FBI is seeking the public's help to stop a suspected child predator known only as John Doe 28.
Investigators said video of the man engaging in sexually explicit activities with a young boy was discovered online in November 2012 by the National Center for Missing & Exploited Children.
The video contains a brief image of the alleged predator, wearing wire-framed glasses and a burgundy T-shirt with a fish logo on it, which investigators hope will lead to his identification and the recovery of the exploited child.
"Subjects who show their faces in child pornography are not typical," said Special Agent Karen Jurden. "It is our hope that someone will recognize this individual and come forward. We were able to recover a very clear image of John Doe 28."
The FBI said the video also shows the individual and the victim inside a residence with what appears to be a blue chair and a picture hanging on a wall in the background. Someone familiar with the house might easily recognize the chair.
There are no details linking the suspect to a particular area, but Jurden said investigators believe he may be a U.S. citizen because he speaks one word during the video -- "careful" -- which is in English.
"Sometimes we will get some type of identifier that narrows down the geographic region," said Jurden, who has been investigating crimes against children for the last four years, "but that didn't happen in this case. That's why we are asking for the public's help nationwide."
The video is just over two minutes long and was recovered during the arrest of a San Francisco man on child pornography charges.
"The video was part of his collection," Jurden added, explaining that sexually explicit videos and images of children are often traded anonymously through online forums.
Investigators said the suspect appears to be white, in his 30s or 40s, with a receding hairline.
Anyone with information is urged to call the FBI's toll-free tip line at 800-CALL-FBI.
"We need to identify John Doe 28," Jurden said, "so we can make sure no harm comes to that little boy."