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An Illinois high school says a "staff member" seen in a viral video calling a student a "piece of sh--" for allegedly wearing a mask improperly has resigned.

The statement to Fox News late Friday from John Mensik, principal of Glenbard North High School in Carol Stream, Illinois, does not identify the employee as a teacher, but says the "staff member" involved in the incident "has resigned and will no longer be working in District 87." 

In the clip posted on social media, a caption over the video reads, "My friend had his mask under his nose, and this Karen went crazy, got up in his face and cuzed (sic) at him."

The footage shows the student asking, "Are you playing?" to a purported teacher at Glenbard North who says, "No, I'm not! Otherwise, I will call the police. I'm serious!" The teacher added, voice cracking, that he has "had enough of it."

The staffer continues to reiterate how serious he is in the video, telling the student, "I knew you were going to take off your mask the moment I turned the corner." He then threatened the student with in-school suspension before telling the teen it was "because you're a piece of sh--."

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In response to the video circulating online, Mensik sent out a notice to parents saying the incident was being investigated and assuring that it would be handled "in an appropriate manner."

Mensik also reminded parents that Illinois Gov. J.B. Pritzker, a Democrat, issued the mask mandate for schools in the state and that it must be enforced. The principal went on to note that ahead of the school year, the Illinois superintendent of schools sent a letter to each district threatening schools that did not enforce compliance with the dictate.

"The letter also stated that schools not following the mask mandate would become unrecognizable by the Illinois State Board of Education meaning that students could lose out on scholarship money, not be able to compete in IHSA athletic programs, and colleges could penalize students for not having an accredited high school diploma," Mensik wrote. 

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He concluded, "Please know that we will continue to follow this mandate and appreciate the cooperation from all staff, students and visitors."