In a federal case involving dozens of children, a former Bemidji assistant school principal was charged with producing and distributing child pornography and the attempted coercion and enticement of a minor.

Brandon Mark Bjerknes, 34, made his first appearance in U.S. District Court in St. Paul on Wednesday. According to the four-count complaint, he posed as a 13- to 15-year-old teen named “Brett Larson” on Facebook and on Snapchat to contact middle school and high school girls and boys. He reportedly engaged in sexually explicit conversations and directed minors to send him sexually explicit photographs.

Authorities say Bjerknes used the alias social media accounts to contact more than 50 minor victims, including students at Bemidji Middle School. Authorities believe there may be other victims and urge anyone with information to call the Beltrami County Sheriff’s Office at 218-333-9111. Callers may remain anonymous.

Bjerknes began work with the Bemidji Area Schools in 2006 and served as assistant principal of Bemidji Middle School until April.

In a search of Bjerknes’ home on March 20, officers seized a number of electronic devices, including his personal and work phones, multiple tablets, computers and external hard drives. The social media accounts and electronic devices contained sexually explicit photos and videos of multiple minor victims, according to the complaint.

The Minnesota Bureau of Criminal Apprehension and the Beltrami County Sheriff’s Office worked jointly on the investigation.