Zimmerman told Hannity he had to shoot Martin when Martin told him he was going to die and made a move for Zimmerman's handgun.
Martin family attorney Benjamin Crump told O'Brien that the state attorney will see the interview as a "gift," because Zimmerman's description of what happened conflicts with the 911 calls from the night of the shooting.
Witness alleges she was abused by suspect in Trayvon Martin killing
Zimmerman, who apologized to Martin's parents during an April bail hearing, again expressed regret Wednesday.
"My wife and I don't have any children. I have nephews that I love more than life. I love them more than myself. And I know when they were born, it was a different unique bond and love that I have with them," Zimmerman told Fox. "And I love my children even though that they aren't born yet. I am sorry that they buried their child. I can't imagine what it must feel like. And I pray for them daily."
Tracy Martin said he had no desire to speak with Zimmerman.
"Absolutely not," he said.
Zimmermans has pleaded not guilty and has been free on $1 million bail since early July. He had been granted bail in April but a judge revoked it after finding that Zimmerman and his wife, Shellie Zimmerman, had failed to disclose more than $150,000 in donations from the public among their assets.
Zimmerman was arrested in April on the murder charge. His wife was arrested on a perjury charge related to the donations in June. Defense attorney O'Mara told Hannity that he could not comment on the donations, given the case against Shellie Zimmerman.
He did say the case against his client would be an appropriate example of a "stand your ground" defense in Florida. Zimmerman said he had not heard of the law before the incident. He also said the media have made a rush to judgment.
Witnesses tell FBI that George Zimmerman is no racist