Skyline High School junior Eric Malone, Jr. used a cellphone camera to record the exchanged with Mark Schaefer during geometry class Monday.
"You got something to f****** say?" the teacher asked in the exchange.
"OK nah, I got something to say ‘cause I'm recording you right now," Malone said.
"Go ahead and record me, b****," the teacher said.
The Dallas Independent School District said the sub's behavior was inappropriate and he will not be returning to Skyline.
"I mean, I admit that I shouldn't have said the things I said, but I've known this kid since he was a freshman," said Schaefer. "He's gotten worse now."
Schaefer told FOX 4's Shaun Rabb that he doesn't blame the school for firing him.
"Principal Wright does the best he can. He's a wonderful principal. I don't blame him a bit for what he did ‘cause what I did was unacceptable," he said.
Skyline's principal apologized to Malone's father for what happened.
"Eric whatever his name is would not leave me alone," said Schaefer. "He wouldn't be quiet. I said, ‘You gotta go. Leave. Go.' Keeps coming back. Finally, I took a picture of him. That's when he turned the video on me. I knew what he was doing. And I said, ‘You know what? I'm pretty p***** off. Anyway, I'm gonna let it go. And so that's when I swore."
Schaefer says his swearing was a spillover from an incident last Friday involving a different student.
"Had a guy this big talking smack to me," said Schaefer. "When my girlfriend called me on the phone, he told her he was gonna [expletive] her…I said, ‘Whoa.'"
"So he took your phone? A student took your phone?" said FOX 4's Shaun Rabb.
"Nah, I let him have it," said Schaefer.
"Your girlfriend called you, you let him have the phone?" said Rabb.
"Yeah," said Schaefer. "Yes."
"That wasn't wise, you think?" said Rabb.
"Well the classroom was completely out of control at that point anyway," said Schaefer.
Schaefer says he challenged that student.
"So when he did that, I said, ‘Wait a minute, wait a minute, wait a minute. I'm gonna f*** him up,'" said Schaefer. "So I chilled out and I beat him at arm wresting just for the hell of it. Then I said, "If you think you're tough, meet me on Forney and Bucker at 4:15, 4:30. He never showed."
Schaefer says he did not report that incident to Principal Wright.
FOX 4 looked for Schaefer Tuesday. He saw our story on FOX 4 News at 9 at his favorite bar.
"If I'd of known that, I wouldn't have gone to the bar," said Schaefer.
Despite the frustration that Schaefer says led to him to "letting go," he said he thinks Skyline High is the best high school in Texas.
The Detroit native, who is a 20-plus year Army veteran with a bachelor's degree in history and a master's in education says that for now, he'll sit down and decide what he'll do next in life.