The FBI is seeking the public's help in catching a man -- known only as John Doe 28 -- who was allegedly caught on video engaging in sexually explicit activities with a young boy.

The video, which is just over two minutes long, was discovered online in November 2012 by the National Center for Missing & Exploited Children and contains a brief image of the alleged predator, the FBI said in a statement issued Tuesday.

"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."

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Officials have enhanced details in the video which they hope will lead to an identification of the suspect and/or the young boy. For example, the video shows the alleged predator and the boy in a residence with what appears to be a blue chair and a picture hanging on the wall in the background. Also, John Doe 28 is seen wearing wire-framed glasses and a burgundy T-shirt with a fish logo on it.

Investigators believe the alleged predator may be a U.S. citizen because he speaks one word -- "careful" -- in the video.

Special Agent Jurden said the video was recovered during the arrest of a San Francisco man on child pornography charges.

"The video was part of his collection," Jurden said, explaining that sexually-explicit videos and images of children are often traded anonymously through online forums.

John Doe 28 is described as a Caucasian male in his 30s or 40s who has a receding hairline. Anyone with information is asked to call 1-800-CALL-FBI.

"We need to identify John Doe 28," Jurden said, "so we can make sure no harm comes to that little boy."