A former Casper resident was sentenced Friday to 25 to 30 years behind bars for sexually assaulting a 4- or 5-year-old boy in the last decade

Derek Alexander McCollum, 32, pleaded guilty in July to the assaults in from August 2007 through 2008. Another count of sexual assault of a minor was dismissed as part of the plea deal.

Before Natrona County District Court Judge Thomas Sullins imposed the sentence, McCollum told the court he was sorry.

"What I did is wrong and I hope one day (the boy) will forgive me for what I've done," he said.

The case began in April 2013 when the boy, now 11, was acting violently and sexually with his classmates where he went to school in another state, according to court records.

Interviews with the boy revealed the abuse started when he and his mother lived in Casper from 2004 to 2007, according to court records.

McCollum has been incarcerated in a prison in Farmington, Mo., 2011 for sexual exploitation of a minor.

He will serve that 10-year term concurrently with the 25- to 30-year sentence at the Wyoming State Penitentiary.

Sullins said he will not be eligible for probation.