A substitute teacher in California was caught on camera lashing out at a 13-year-old student wearing a pro-police thin blue line face mask, saying it’s the new version of the Confederate flag. 

"That’s not the American flag, that’s the new confederacy flag," the substitute teacher said in the video to a student at Lyman Gilmore Middle School in Grass Valley.

Lucas Lillar, 13, was wearing a thin blue line face mask last Monday in a math class when the "unprovoked" verbal altercation unfolded. His father and stepmother are both in law enforcement and Lillar often wears the face mask. 

Photo of Lucas Lillar

Photo of Lucas Lillar (Fox & Friends Weekend)

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"I never had someone talk to me like that, yell at me in my face, especially a teacher," Lillar told CBS13

The video was recorded by students in the class and soon surfaced on social media. 

Screenshot of altercation between California substitute teacher and 13-year-old student over thin blue line face mask (Fox & Friends Weekend)

Screenshot of altercation between California substitute teacher and 13-year-old student over thin blue line face mask (Fox & Friends Weekend) (Fox & Friends Weekend)

"Well, we can’t do the Confederate, but we can put up the red, white and blue. No, it’s black, white, with some blue line in it," the teacher continued in the video. 

"Yeah, it’s got the thin blue line," Lillar shot back.

"Yeah, but it’s not American," the teacher responded.

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Lillar told "Fox & Friends Weekend" that the back-and-forth lasted about 20 minutes, and ended once the school bell rang for classes to change. The altercation also left Lillar confused, explaining he’s "not too sure what [the teacher's] point was."

"I was confused because I didn't know what he was talking about at first. And then he kept saying that is un-American and how if police don't like you though, they’ll shoot you."

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Lillar’s mother, Amanda McCallum, told "Fox & Friends Weekend" that she spoke with the principal and the district’s superintendent who assured her the teacher would not be able to teach in any of the schools in the district again. 

Screen shot of Lucas Lillar and mother Amanda McCallum (Fox & Friends Weekend)

Screen shot of Lucas Lillar and mother Amanda McCallum (Fox & Friends Weekend)

"The next step that we're working on is putting statements together so that he can not teach again in the state," she said. 

Scott W. Lay, the Nevada County Superintendent of Schools said the incident is under investigation.

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"The incident is currently under investigation, and we will take appropriate action. The California Education Code §44953 allows for immediate dismissal of a substitute teacher. We expect all educators to perform their duties with utmost respect and professionalism to afford our youth an environment conducive to learning. The California Commission on Teacher Credentialing that governs educator credentials will be informed of this incident," Lay said in a statement to CBS13.