A Minnesota man and former substitute teacher pleaded guilty to child pornography and extortion charges on Monday.

According to federal prosecutors, Mitchell James Ottinger, 25, ran a years-long “sextortion” scheme targeting both minors and adults “by adopting false female personae, including of minor girls.”

The defendant also allegedly threatened “to disseminate sexually explicit images and videos of his victims in order to extort more images and videos from them,” according to the plea agreement filed in the U.S. District Court for the Minnesota District on Monday.