ANCHORAGE, Alaska (AP) — A former teaching assistant in Anchorage will spend up to 15 years in prison for possessing and distributing child pornography.

34-year-old Daniel Allan Brown was also sentenced Friday to lifetime supervision. Investigators say they found over 40,000 images and videos of child pornography on his computer.

Authorities began investigating Brown after he started trading images with an undercover agent in New Zealand. Assistant U.S. Attorney Kyle Reardon says Brown took pictures of students that were not pornographic and used some as avatars on websites where he traded illicit images.

Reardon says Brown will serve at least 12 years and six months before becoming eligible for release.

Brown was a substitute teacher in the Anchorage School District and at Huffman Elementary. He worked with special education students.