A teenage fugitive from Texas known for using an "affluenza" defence is to be returned to the US along with his mother, after a mobile phone used to order a pizza gave away their location at a Mexican resort.
Dee Anderson, sheriff of Tarrant County in Texas, said Ethan Couch, 18, who was on probation after killing four people in a drink-driving rampage, and his mother Tonya had prepared to be gone a while, even dyeing Couch's blond hair black, before being detained in the Pacific Coast city of Puerto Vallarta.
"They had planned to disappear. They even had something that was almost akin to a going-away party before leaving town," Mr Anderson said. He would not give details about the event, including how many people attended.
In June 2013, a drunken Couch was speeding on a road south of Fort Worth when he crashed into an SUV at the side of the road, killing four people and injuring several others, including passengers in his pick-up truck.
He pleaded guilty to four counts of intoxication manslaughter and two counts of intoxication assault causing serious bodily injury. A judge sentenced him in juvenile court to 10 years' probation and a stint in a rehabilitation centre.
Authorities had begun searching for Couch and his mother after he missed a mandatory appointment with his probation officer on December 10.
During the sentencing phase of Couch's trial, a defence expert argued that his wealthy parents coddled him into a sense of irresponsibility - a condition the expert termed "affluenza". The condition is not recognised as a medical diagnosis by the American Psychiatric Association and its invocation drew ridicule.
Couch disappeared as authorities investigated whether he had violated the terms of his probation.
Mr Anderson said Couch and his mother apparently crossed the border in her pick-up truck and drove to Puerto Vallarta. It was not clear whether they had any accomplices.
No immediate charges were planned for others who may have known about or assisted with the flight plan, Mr Anderson said. He said authorities had no evidence that Couch's father, who owns a sheet metal factory in North Texas, was involved.
Jalisco state prosecutor Eduardo Almaguer Ramirez said US authorities knew the mother and son were in Puerto Vallarta because of a phone call to Domino's Pizza.
A US Marshals Service agent tipped authorities in Mexico to the location of the phone, according to a police report issued by the Jalisco state prosecutors' office. The phone had been used to order pizza for a room at a condominium complex.
When agents arrived the Couches had already moved on, but a tourism operator pointed them to the mother and son's new home at an apartment in Puerto Vallarta's old town. Agents set up a surveillance operation in the area and found the Couches that night.
The police report says they claimed to be carrying no identification and gave inconsistent stories about their names. They were taken into custody and handed over to immigration officials.
Mr Anderson noted that Ethan Couch's hair was "markedly different". A photo distributed by the Jalisco state prosecutors' office shows him in detention with his hair dyed black and his normally blondish beard now brown.
The sheriff has said he believes the Couches fled in late November after a video surfaced that appears to show Couch at a party where people were drinking. If found to be drinking, Couch's probation could be revoked and he could face up to four months in jail.
Once returned to Texas, Couch will be held in a Tarrant County facility until a probation violation hearing next month.
Mr Anderson said an arrest warrant was being issued for Tonya Couch on charges of hindering an apprehension, a third-degree felony that carries a sentence of two to 10 years in prison. Tarrant County district attorney Sharen Wilson said she planned to ask a judge to transfer Ethan Couch's case to adult court.
Couch would then face up to 120 days in an adult jail, followed by 10 years' probation. If he violates probation, he could face up to 10 years in prison per death, Ms Wilson said.
If the judge refuses to transfer Couch to adult court, Ms Wilson will ask that his probation be revoked, in which case he could be held in a juvenile detention centre until his sentence expires when he is 19 in April.
Couch's lawyers, Scott Brown and Reagan Wynn, said they would not comment until they has spoken to him, probably not before Couch reaches the US.
Ricardo Ariel Vera, the representative of Mexico's immigration institute in Jalisco state, said the mother and son were being held at immigration offices in Guadalajara and would be returned to the United States aboard a commercial flight to Houston.
"They are going to be sent back to their country, given that they were in Mexico improperly," he said. "They would have had to enter, for example, as tourists, but they entered without registering."