An Oklahoma man was sentenced to 40 years in prison Monday after being found guilty in U.S. federal court of sexually abusing children while he volunteered at a Kenyan orphanage.

Matthew Lane Durham, 21, of Edmond, Oklahoma, was convicted by a jury in June for "engaging in illicit sexual conduct in foreign places."

In April 2014, when he was 19, Durham had traveled to the Upendo Children’s Home in Juja, about an hour outside of the Kenyan capital, Nairobi, to volunteer for the fourth time. While there, he sexually assaulted at least three girls — ages 5, 9, and 15 — and a 12-year-old boy.

Durham was alleged to have confessed to the abuse while in Kenya, but was able to leave the country before local authorities could bring charges.

However, U.S. federal law gives American courts jurisdiction over certain sex crimes committed by citizens against minors abroad.

Indicted in August 2014, Durham pleaded not guilty at trial and blamed a demon for making him do "horrible things."