Larimer County Sheriff Jim Alderden announced at a press conference on Sunday that Colorado authorities have ruled the "balloon boy's" flight a hoax.

"It has been determined that this is a hoax. We believe we have evidence at this point to indicate that this was a publicity stunt," Alderden told reporters.

Authorities believe the alleged plot was hatched in an attempt by the Heene family "to better market themselves for a reality show at some point in the future," Alderden said. "They were lying."

The Larimer County Sheriff's Office will recommend charges of conspiracy, contributing to the delinquency of a minor, false reporting to authorities, and attempting to influence a public servant against the Heenes.

No charges have been filed yet, and neither Richard or Mayumi Heene are under arrest. Some of the most serious charges each carry a maximum sentence of six years in prison and a $500,000 fine.

Alderden said all three of the Heenes' sons knew of the balloon hoax, but likely won't face charges because of their ages. One of the boys told investigators he saw his brother get in the balloon's box before it launched.

Authorities believe the family planned the hoax for at least two weeks prior to Thursday's saga. "On the bizarre meter, this rates a 10," Alderden said.

"These people are actors. Not only have they appeared in several reality shows...the way they established their relationship was at an acting school in Hollywood. They put on a very good show," Alderden said. "Clearly we were manipulated by the family."

Acknowledging that the media grew wary of the Heenes' story before Sunday's announcement, Alderden insisted that his office built an investigation based on facts.

"There was a lot of skepticism, a lot of conjecture," Alderden said, "but we have to operate on facts." Officials, alarmed by a series of bizarre television interviews given by the Heene family, carried out an investigation with "the goal of getting a confession" from the family, Alderden said.

Richard Heene, while shopping with his wife and three sons at Wal-Mart, told the media on Sunday afternoon that the balloon saga and the media coverage had become "so convoluted."

Richard Heene says he's "seeking counsel," though it was unclear whether he was talking about hiring an attorney. Heene says his wife is holding together better than he is.

Richard and Mayumi Heene met with Larimer County investigators for much of Saturday afternoon to discuss Thursday's events, during which they claimed their six-year-old son Falcon vanished into the rafters of his garage while the world thought he was zooming through the sky in a flying saucer-like helium balloon.

Suspicion that the balloon saga was a hoax arose almost immediately after Falcon was found hiding in a cardboard box. Heene, a storm chaser and inventor whose family has appeared on the reality show "Wife Swap," and his wife had said one of the boy's older brothers had told them that Falcon was aboard the homemade balloon when it took off.

Alderden initially said there was no reason to believe the incident was a hoax. Authorities questioned the Heenes again after Falcon turned to his dad during a CNN interview Thursday night and said "you said we did this for a show" when asked why he didn't come out of his hiding place.

But an anonymous student told Web site The Business Insider that he worked with Heene in 2009 on potential reality show proposals to pitch to ABC.

The student said he and Heene pitched a show that would include several pranks, one of which was similar to the high-flying balloon incident, according to The Business Insider.

Falcon got sick during two separate TV interviews Friday when asked again why he hid from his family.

After the sheriff spoke to reporters, Richard Heene and his wife walked out of his office after meeting with officials for several hours. As reporters yelled questions, all Heene said was, "I was talking to the sheriff's department just now." He then walked to his car with his wife and a friend, and they drove away.

Child Protective Services had also reportedly been asked to interview the Heene family and Alderden said they would "probably open an investigation."

He called the move to contact CPS 'standard' in cases involving children.

It wasn't clear where the family was late Saturday night. By 9 p.m., an Associated Press reporter at the family home said the couple hadn't returned after leaving the sheriff's office. Their three sons were believed to have been at home being watched by sheriff's officials earlier in the day, but their whereabouts also weren't known to reporters in the evening.

The day began with Richard Heene knocking on the windows of journalists camped outside his home and promising a "big announcement." A few hours later, he did an about-face when he told reporters that they should leave questions in a cardboard box on the front doorstep.

As Heene walked away, a reporter shouted, "Can you tell us once and for all if this is a hoax?"

"Absolutely no hoax. I want your questions in the box," Heene said, waving a cardboard container before going back into his home.

A circus-like atmosphere formed outside, including men holding signs and occasionally yelling "balloon boy." One sign read, "Put balloon boy on TV: America's Most Wanted."

Other gawkers carried aluminum-foil stovetop popcorn makers that resembled the a flying saucer-like helium balloon launched from the family's backyard Thursday, with 6-year-old Falcon Heene believed to be onboard.

The Heenes have said the balloon was supposed to be tethered to the ground when it lifted off, and no one was supposed to be aboard. A video of the launch shows the family counting down in unison, "3, 2, 1," before Richard Heene pulls a cord, setting the balloon into the air.

"Whoa!" one of the boys exclaims. Then his father says in disbelief, "Oh, my God!" He then says to someone, "You didn't put the (expletive) tether down!" and he kicks the wood frame that had held the balloon.

Falcon's brother said he saw him inside the compartment before it took off and that's why they thought he was in there when it launched. Heene said he had yelled at Falcon before the launch for getting inside.

Over the years, Richard Heene has worked as a storm chaser, a handyman and contractor, and an aspiring reality-TV star.

He and his family appeared on the ABC reality show "Wife Swap," and the show's producer said it had a show in development with the Heenes but the deal is now off. TLC also said Heene had pitched a reality show to the network months ago, but it passed on the offer.

Despite his attempts to get on TV, Heene insisted Saturday that he didn't know what kinds of questions were being asked about him because he didn't have cable.

"I'm going to place the box out front. Please write your questions down, because friends are telling me they're saying this and that. I have no idea what the news is saying," Heene said.

The Associated Press contributed to this report.