Before making their way to Mexico’s Pacific coast, where they were eventually detained, “affluenza teen” Ethan Couch and his mother threw themselves a party, officials said Tuesday. Later, as the duo drove south, police received “dozens and dozens of calls of sightings” of them or their truck.

Citing the Jalisco State prosecutor’s office, the New York Times reports that the Couches were arrested Monday evening in Colonia 5 de Diciembre, a neighborhood popular with American tourists in Puerto Vallarta, a Mexican resort town. Because they were in Mexico illegally, the prosecutor’s office said, they were turned over to the National Institute of Migration. They are expected to be returned to the United States.

The Couches had had some unfinished business to tend to before making their way across the border, however. “We learned through some interviews that what we suspected all along had happened, that they had planned to disappear, that they even had something that was akin to a going-away party before they left town,” Tarrant County sheriff Dee Anderson said at a news conference Monday. This indicated to investigators that Couch’s disappearance “was carefully planned and timed to get out of the country.”

In 2013, Ethan Couch—who has died his blond hair and red facial patches dark brown—was sentenced to 10 years probation after admitting to four counts of manslaughter in a drunk driving incident that left four people dead. (Couch was 16 at the time.) He is wanted for violating the terms of that probation.

Since the time of the incident, Sheriff Anderson said, it has been clear that his mother, Tonya Couch, did not believe that her son needed to be punished. (After all, it’s her fault he had affluenza in the first place.) “There’s just no chance that she will ever think he needs to be punished or held accountable,” the sheriff said. A warrant has been issued for her arrest for hindering apprehension.

Officials don’t believe that Couch’s father—who is divorced from his mother (and who was arrested last year for impersonating a police officer)—assisted in their escape. Plenty of people assisted the police, though: Investigators received “dozens and dozens of calls of sightings” from people who knew the Couches, Anderson said.

From the Times:

Investigators received helpful information from people who know the Couches, and “dozens and dozens of calls of sightings” of them or their pickup truck, he said. The pair are believed to have driven the truck from the Fort Worth area deep into Mexico, but he would not say whether they still had it with them, or how they supported themselves on the run.

“He was, at best, looking at a life of exile,” Sheriff Anderson said of Mr. Couch.

A crucial piece of information indicating that they were in Puerto Vallarta came on Dec. 24, the sheriff said, but he would not elaborate. “The problem with it was, as you can imagine, Puerto Vallarta at Christmas time, a tremendous amount of tourists down there, so American people were prevalent everywhere, it wouldn’t be somewhere they were going to stick out,” he said.

Jalisco state officials said that the Marshals Service, through the American Consulate in the state capital, Guadalajara, asked local authorities to search for the Couches in Puerto Vallarta.

Texas prosecutors have been trying to move Couch’s case to adult court for some time. At a news conference Tuesday, Tarrant County District Attorney Sharon Wilson said her office would take this opportunity to make that change, before Couch turns 19. “We no longer have to be concerned about the best interest of the child,” she said.

If Couch’s case remains in the juvenile system, NBC News reports, he could end up spending just a few months in jail, as Texas usually releases incarcerated juveniles when they turn 19. (Couch turns 19 in April.) “We can move him to adult court,” said Wilson, “and an adult judge can instate or enforce his 10-year probated sentence that was given to him before—which means he’d be on additional eight years probation.”

The sheriff echoed the DA’s sentiments. “I personally felt like justice was denied at the first juncture, and I had everything possible invested in this to get him back and I’m not apologizing for it,” Anderson said. “I don’t believe that the community and the public wanted anything less than us to use every available means to bring him back.”

A hearing has been scheduled for January 19th.

Images via Jalisco State Prosecutor/Marshals Service/AP Images. Contact the author of this post: brendan.oconnor@gawker.com.