LAMOURE COUNTY, N.D. (VNL) – A Kulm, N.D. man will spend two decades in jail after he pleaded guilty to sexually assaulting a young boy last summer.

18-year-old Zachary Richardson was charged with one count of felony gross sexual imposition.

LaMoure County Attorney James Shockman says Richardson must first serve at least 12 years behind bars, and the remainder of his 20-year sentence will be spent on supervised probation.

Court documents say when officers interviewed Richardson’s foster mom on Aug. 13., she told investigators that Richardson has had several assessments and placements into treatments for psychological and social disorders. She said many of Richardson’s therapists and social workers have said Richardson should not be in public alone. Documents say Richardson’s therapists said that Richardson would sexually offend young children if given the chance.

Richardson’s foster mom told officers she had taken away all of Richardson’s electronics as he was regularly engaging in sexual and pornographic sites.