"I met some dudes and we went to a bonfire," the Masterton man told the show. "There was a commotion with two of them and one of them stabbed the other one and he ended up passing away."
Brider admitted he served six years in prison but no further context was given to the story.
The talent show's judging panel liked his reggae version of Eminem's The Real Slim Shady and he was accepted to the bootcamp phase. He told the Wairarapa Times-Age he had been honest with the show's producers about his criminal past and was not looking for sympathy.
"Since the jail sentence I used to get so far then there's another wall put there, and then again and then again and then again. Today it's just another wall to tear down.
"I don't need to be reminded by headlines and stuff about what happened. I know what I did and all I need from the public is support. I'm not looking for pity or forgiveness, just support."
Jeremy Frew's mother, Donna Travers, said the family should have been notified the episode was going to air and ensured the facts were told correctly. "It's devastating for us, it revictimises us. My sister and my daughter were watching it and they had no idea it was going to be on.
"What really got to us the most was that he said Jeremy was his friend. That was the worst thing that guy could have said. My son was scared of him and his mates and he said it on the day he was killed."
Ms Travers, who moved to Australia after Jeremy's death to deal with the tragedy, has complained to TV3 and wants it to broadcast an apology and the facts of the case.
"Shae Brider lied. It's not the fact he's on X Factor - he can do whatever he likes - it's that they should have checked all the facts of what he said."
Media commentator Jim Tully said colourful contestant back-stories were part of TV talent shows, but in Brider's case it was the way facts were "fudged over" that was an issue.
"If you're going to have contestants with backgrounds that are going to be seen to be problematic for the public I think you've got an obligation to be totally up front and for the situation to be explained as fully and as candidly as possible."
Brider said he moved to Masterton out of respect to his victim's family, and prison was life-changing for him.
Apart from a driving offence, he had remained clear of convictions since his release.
Now married, he works at a Masterton service station, where he said customers supported him.
MediaWorks refused to answer specific questions about Brider, including whether other contestants or the judges were notified of his past.
In an emailed statement, a spokeswoman said the show did not intend to upset Jeremy's family.
"However, it is important to note the New Zealand justice system judges Shae has paid his debt to society ... "