A man accused of killing a teenage student over an affair with his teacher wife says he knew "for a long time" she was having an affair, but refused to believe it.

"I pretty much knew. I think I was just in denial for a long time, you know," Eric McLean, 31, said in a jailhouse interview which was to be aired Thursday on NBC's Today Show.

McLean is charged with first-degree murder in the March 10 shooting death of Sean Powell, 18, a former West High student who met Erin McLean last fall during her teaching internship at the school. McLean supported his family as a pizza deliveryman while working to complete his college degree so he could become a school band director.

General Sessions Judge Bob McGee agreed Wednesday to allow the NBC interview over prosecutors' objections that it could prejudice a jury pool. Defense attorney Bruce Poston argued for the interview, saying it would be the only one he would allow before trial.

McLean surrendered on March 11 to a police officer who approached him walking along railroad tracks six miles from the high school, according to court affidavits obtained by The Associated Press on Wednesday. McLean identified a rifle near the tracks as the murder weapon.

"McLean stated that he had learned of an adulterous affair between his wife and the victim several weeks prior to the murder," Knoxville police investigator Andrew Boatman wrote.

McLean shot Powell after finding him at his house and telling him to leave, Boatman's affidavit said. McLean called 911 to report and intruder and called back saying to disregard the call "because the intruder was leaving," according to the affidavit.

McLean "stated that he felt a great amount of stress due to his wife's relationship with Powell," the investigator wrote. "McLean stated that he went to his Toyota truck parked in the street in front of his house and retrieved a rifle and that he remembered shooting Powell."

Powell died from a shot in the head as he sat in his car outside the McLeans' home.

After the shooting, Erin McLean, 29, reportedly went to Nashville with their two sons to stay with relatives. Four days after the murder, paramedics rushed her to Centennial Medical Center after she tried to commit suicide with prescription drugs, according to police spokeswoman Kristin Mumford. She was released the next day, according to hospital records.

Poston said he would seek emergency custody of the children on behalf of Eric McLean's parents because there are "legitimate concerns regarding their safety."

Eric McLean faces a bond hearing on Tuesday.