Richard Heene (C), his wife Mayumi (R) and son six-year-old Falcon Heene talk to reporters in Fort Collins, Colorado, October 15, 2009. REUTERS/Rick Wilking

DENVER (Reuters) - The mother of a Colorado boy thought to be aboard a homemade helium balloon has admitted to investigators the whole thing was a hoax, according to a court document made public on Friday.

The local sheriff had already said the October 15 “Balloon Boy” incident was a publicity stunt and expected felony charges to be filed against the 6-year-old boy’s parents, Richard and Mayumi Heene.

The live television images of the silver saucer-like balloon soaring through the Colorado skies captivated audiences until the boy turned up in the family’s attic. Public sympathy turned to outrage when the family’s account began to unravel.

According to a copy of a search warrant affidavit posted on the website of Fort Collins newspaper “The Coloradoan,” Mayumi told investigators she and her husband lied to authorities and knew their son Falcon was at home as rescue teams tracked the balloon believing the boy was inside.

“The motive for the fabricated story was to make the Heene family more marketable for future media interest,” the affidavit states.

The document also says the Heenes, who had starred in the reality television show “Wife Swap,” had devised the hoax about two weeks before and had instructed their three children to lie to authorities and the media.