A 57-year-old Hawaii island man who admitted to producing pornographic images of himself and two children under 10 years old told a federal judge Monday, "I’m never going to repeat this ever again. This is not a hope. I’m giving you a guarantee."

The judge told John Ridgely Tucker that he did an "unspeakable act," and sentenced him to 20 years in prison.

U.S. District Judge Susan Oki Mollway also told Tucker that when he is released from prison, he will have to register as a convicted sex offender and submit to probationlike court supervision for the rest of his life.

The FBI began an investigating after it received digital images from the National Center for Missing and Exploited Children. The images, which had been circulating on child pornography websites, showed an adult male with two children.

The FBI made public a picture of the man last October after it enhanced the background of one of the images and spotted a Hawaii island telephone directory.

Within hours, callers identified the man as Tucker, operator of a bed-and-breakfast in Pahoa.

A FEDERAL prosecutor said the FBI searched Tucker’s home and found the same images on his computer. Agents also located the children, who identified themselves and Tucker in the images.

Tucker pleaded guilty to one of six charges of sexual exploitation of minors against him. All of the charges alleged that he committed the crimes in or around 2008.

Assistant U.S. Attorney Les Osborne said the charges were based on 15 images the FBI recovered. He said the exploitation of at least one child occurred over a period of time because in one image the child’s hair is in bangs and in a later image the child’s hair is long.