SYRACUSE, N.Y. -- A North Country man has pleaded guilty to federal sexual exploitation charges related to the kidnapping two Amish girls last summer, and exploitation of other minors.

Prosecutors say Stephen Howells II and his girlfriend Nicole Vaisey kidnapped the girls from their family's farm stand in St. Lawrence County last August. The girls were returned home about 24 hours later after a statewide Amber Alert was launched, and the story went worldwide.

Howells pleaded guilty all 21 counts, including conspiracy to produce child pornography, producing child pornography and possessing child pornography. The conspiracy and 15 additional counts relate to Howells’ sexual abuse of six children, ages 5-11, and his filming of that abuse on 16 dates between December 2012 and August 2014, federal prosecutor said.

Howells also pled guilty to five counts of possession of child pornography separate from the children. These counts relate to numerous image and video files Howells collected from the Internet.

Each count carries a sentence of 15-to-30 years in jail. During court Friday, there was a detailed account of the sexual acts against the young girls by Howells and Vaisey that had been recorded and stored on computers and marketed for sale.

In court, Howells admitted that from September 2013 to August 2014, he and Vaisey consipired to produce child pornography. He said he used his job as a registered nurse to obtain drugs to sedate the children, according to a release from the U.S. attorney’s office.

“The criminal conduct committed by Stephen Howells is beyond comprehension,” saiod U.S. Attorney Richard S. Hartunian. “Our hearts go out to all the young victims who endured his unspeakable acts. We will continue to do everything in our power to see that he will never abuse another innocent child. I commend the community, the St. Lawrence County Sheriff’s Office, the New York State Police, and the Federal Bureau of Investigation for working tirelessly to bring him to justice.”

Sentencing for Howells on the federal charges is scheduled for September 18.

Vaisey still faces similar charges, and has a court date scheduled for June.

Neither Vaisey or Howells have been tried on the local charge of first-degree kidnapping, or other charges that would be tried in St. Lawrence County court related to the kidnapping itself, including allegations that the two young girls were assaulted.

Time Warner Cable News will bring you more information as it becomes available.