Hagan was caught on camera by another student in his classroom. April Carr, mother of the student who was targeted by Hagan, uploaded the video onto Facebook Monday.
"You screw with me you're going to be in big ass trouble," Hagan is heard saying in the video. "Don't smile at me. That's how people like you get shot."
But the bizarre remarks didn't stop there; rather, this was just the tip of the iceberg.
"I got a bet," Hagan continued. "I bet by the time you're 21, somebody's going to put a bullet in your head. OK. And it might be me the one who does it."
According to Carr's 17-year-old son, Hagan went off the rails after a group of students in the classroom, himself included, laughed while the instructor was writing an equation on the board, WSB-TV reported.
"I think it's a terroristic threat on my son's life that I definitely don't take lightly," Carr told the news station. "I mean, I was outraged."
Carr has since initiated a petition to have Hagan fired.
"This is unacceptable from anyone, but especially from the educators we trust to teach our children and help them grow," Carr wrote on the campaign site. "I am demanding he be released from his position immediately."
Both school and police officials are investigating the matter — law enforcement became involved after Carr filed a police report.