The movie star, who teamed up with the soul singer in The Bodyguard, admits he was floored when a party guest told him the tragic news two years ago (Feb12) and he decided to put his thoughts and feelings on film.
During a taped appearance on The Ellen DeGeneres Show, which was set to air in America on Friday (14Feb14), Costner revealed, "My friend was videotaping the party and I said, 'Come down to the back of the house and just put the camera on,' and I started talking to him about her (Houston)."
The actor admits he has no idea where the footage is because he has never seen it since. It was just a therapeutic moment that allowed him to get his feelings out.
He adds, "I was done."
Costner then refused to be part of the media circus that followed Houston's death - because he had already said what he needed to say during that quiet moment at his son's party.
He explains, "There was kind of a steady drumbeat: 'Where is Kevin?' and finally it got to that kind of uncomfortable thing - 'Do I need to go out and say something?'"
Costner finally broke his silence when he delivered a heartbreaking eulogy at his late friend's memorial service.