The Osakis, Minn., School District is investigating allegations that bullies tied up a high school student with an electrical cord during class while a teacher failed to intervene.

Superintendent Joseph Broderick said the administration and school board "are aware of the allegations and … we're going to do our due diligence and investigate it."

On Friday, Nicolette Rochefort posted a picture of her 15-year-old son with his hands tied behind his back and cords wrapped around his neck over a hooded sweatshirt. The boy, a student at Osakis High School, is shown sitting on the floor. Rochefort said she discovered the picture on Snap Chat.

"Bullies did this to my son today at school in a classroom with a teacher present who did nothing about it for 40 minutes," Rochefort wrote in a Facebook post that was shared by more than 17,000 users by early Tuesday evening.

Rochefort told other media outlets that her son had been repeatedly harassed by upperclassmen.

Osakis Police Chief Chad Gulbranson told the Osakis Review that the Douglas County Attorney's Office decided not to press charges after his investigation.

"As horrible as the picture looks, it was determined that there was nothing criminal involved," he told the newspaper. Gulbranson said it appeared that the young man chose to be involved in the act.

Maya Rao