The View host Barbara Walters relayed a conversation she had with Mariah after the altercation.
"She said that when Nicki walked off the set, multiple people heard Nicki say, 'If I had a gun I would shoot the b----,'" Barbara said.
According to Mariah, Idol hairdressers, producers and other staffers heard the threat.
"She said she's very concerned. She doesn't feel that anything would happen, but Nicki is unpredictable, and Mariah says she can't take a chance and she has hired extra security," Barbara continued.
Mariah added that the 29-year-old colourfully wigged rapper has not apologised to her yet, only saying, "I love you, but we might fight again", according to Barbara's story.
Nicki took to Twitter to deny the comment.
"Hey y'all [sic]. Let's just say Nicki said something about a gun. People will believe it 'cuz she's a black rapper. Lmao. I'll then hit up Barbara n milk it [sic])," Nicki wrote.
"Ironically no camera or mic heard the gun comment though. Lol @ the struggle. Not even the producers believed u. Say no to violence barbz."
"Barbara Walters didn't reach out from our team barbz. I guess we're too dangerous. Don't shake if u don't wanna get shook!!!! LmAooooooooooo [sic]."
And then came a zinger aimed directly at Mariah herself.
"I guess it hurts to have the producers tell u to your face that Nicki is the best judge we've had since Simon [Cowell]," Nicki tweeted.
"Awww, poor you. Keep them lies cmn [sic]."
So much for keeping the peace. However, Daily Mail reports that the judges kept it civil the day after the incident (yeah right).
Earlier this week, Idol producer Nigel Lythgoe denied Nicki's alleged death threat.
"The statement is absolute rubbish. It's absolutely not true in any way, shape or form," Nigel said.
In the leaked video, Nicki was caught on tape calling the 42-year-old 'Dreamlover' singer "her f---ing highness".
According to TMZ, Nicki thinks producers made Mariah start a conflict on set.
Meanwhile, Aussie judge Keith Urban told Extra he felt like "the UN" trying to keep the peace between his co-judges.
"I love it, I gotta say. I love working with passionate people. I love artists," he said.
"Everyone just sort of expressing themselves. It's a very alive and very invigorating work environment."
That's one way to put it.
In pics: 10 reasons you should never ever go on reality TV.