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DALLAS (CBS11) – New York Times best-selling author Frank Ahearn has made a living finding people who don’t want to be found.

He wrote “How To Disappear,” and we spoke with him at his apartment in Paris, where he heard about the disappearance of Ethan Couch and his mother Tonya.

Ahearn believes it won’t take long to track down the pair because disappearing takes planning.

“You need to find a safe haven and that’s not exactly easy to do,” says Ahearn.

He believes Couch and his mom decided suddenly to leave town after a video appeared online showing the 18-year-old at a party.

Experts say that may have been a violation of his sentence, a ten year probation for killing four people during a drunk driving crash in 2013.

Ahearn says, “I think they just responded to the situation he’s probably going to go to jail, let’s disappear. I don’t think they really had a plan laid out.”

Tarrant County Sheriff Dee Anderson says Couch showed up to his probation officer immediately after the video of him at the party first surfaced.

But Sheriff Anderson says he believes Couch and his mom skipped town right afterwards, gaining a ten to 14 day head start.

Couch didn’t check in with his probation officer during the next required visit.

Once authorities discovered that, Sheriff Anderson asked the U.S. Marshals to help find Couch.

The FBI in Dallas has also offered to help.

On Tuesday, Sheriff Anderson said he and the U.S. Marshals have received a lot of tips from people across the country, a day after they released a photo of a pick-up truck belonging to Couch’s mother.

Sheriff Anderson says because Couch’s family is wealthy, they may have left the country.

If so, Ahearn says Mexico is the most likely destination. “Even if they drove into Mexico with a bag of cash, that cash is going to run out, they can’t hit their credit cards, nobody is going to Western Union them some money. They’ll end up with no cash to survive.”

Ahearn says with the Couch story getting so much attention it will be difficult for the two to stay hidden.

He also says they likely left behind clues without realizing it.

“A lot of times people don’t think about what they’re doing online, so they may just look up maybe I’ll go to Belize and look up pictures of Belize or something.”

Ahearn says one place that can be difficult to track people down is in the islands.

“You can island-hop and travel via boat, via plane, but I don’t think they’re that savvy.”

For people to successfully disappear, Ahearn says they need to blend into their surroundings and get a job so they can earn money to survive without being detected.

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