MUNCIE, Ind. (AP) — A former Ball State University math instructor has been has been sentenced to four years of probation on his convictions of child pornography and other charges stemming from his alleged use of a campus computer to access images of nude children.

Fifty-year-old Brian Kenneth Siebenaler also will be required to register as an offender against children. He was convicted last month of four counts each of child exploitation and possession of child pornography.

The Star Press reports Siebenaler apologized Wednesday for his actions, saying that while he never met the children shown in the images he collected, “my actions undoubtedly caused additional harm” to them.

Siebenaler was arrested in March 2016 after campus police received an alert someone was accessing child pornography on a computer in a classroom building.