A 21-year-old Oklahoma man was sentenced on Monday to 40 years in prison for sexually assaulting orphaned children while on a missionary trip in Kenya in 2014.

Matthew Lane Durham was found guilty on four counts of "engaging in illicit sexual conduct in foreign places" in June, BuzzFeed reports. A federal judge sentenced Durham this week to 40 years in prison, and ruled that he must pay the victims $15,863 in restitution.

"In a span of just 33 days," prosecutors wrote, per CNN, Durham "raped three girls -- ages 5, 9 and 15 -- at least eight times. During that same time period, he sexually molested a 12-year-old boy twice." They added that Durham "not only forcefully sexually abused these children," but "he psychologically damaged them by taking advantage of their trust he received from the children."

Durham was a volunteer with the Upendo Children's Home in Nairobi between April and June 2014, according to the Chicago Tribune.

"Other volunteers must now live under the cloud of suspicion, distrust and apprehension when they volunteer their time, talent and resources for the betterment of children in East Africa and beyond," prosecutors wrote.

Durham apparently requested to stay at an “overflow bunk” in the school instead of at an off-site location with other volunteers so he would be in a “better position to assist the children,” according to CNN.

In June, Durham ― who pleaded not guilty after his arrest in 2014 ― denied assaulting any of the children, despite having previously confessed on video, Oklahoma news channel KFOR reported. Durham testified that he thought he was possessed by a demon named Luke who did “horrible things,” and said he struggled with his sexuality.

“All I wanted was to follow God’s plan for me,” he told the courtroom on Monday. “In the end, it is the judgment of God that is central, not the judgment of man. I do not fear God’s judgment of me.”

CORRECTION: A previous version of this article included a link, cited by a prior source, to a similarly named children’s home in Kenya that is not affiliated with the Upendo Children’s Home. We regret the error.