Police said Esterly and Amy exchanged hundreds of text messages and her mother later said it sounded like her daughter was texting a boyfriend. They were involved in a secret relationship, officials previously said.
Amy has been safely returned to her family in Pennsylvania, according to a statement from Immigration and Customs Enforcement (ICE) and Homeland Security investigators.
March 8: Allentown police become aware that Yu and Esterly flew to Cancun, Mexico, but they keep this quiet to avoid tipping off either of them that authorities are closing in on them.
Both were smiling as they were taken into custody - Kevin in handcuffs, Amy in a vehicle.
"Amy's been known to the family for like eight years", John Waldron, an attorney representing Kevin Esterly's wife, Stacey Esterly, reportedly told the news station. The disappearing acts got so bad that, at one point, Esterly was prohibited from being on the grounds of Lehigh Valley Academy Regional Charter School.
Authorities said he withdrew $4,000 from his wife Stacey's bank account and signed the youth out of the school-falsely claiming to be her stepfather.
"For two weeks, I've had trouble sleeping and eating", Lu told police when Yu was found.
Authorities say Esterly was placed into custody by Mexican authorities, and Yu was found unharmed and in good health. When police find the Esterlys there, officers tell the Esterlys to go and never come back.
Esterly is expected to be turned over to Miami Police Department and then extradited to Allentown where he is facing a felony charge of custodial interference.
It was also around early February that Esterly and his wife, Stacy, went to Amy's house.
Police say Esterly signed the teen out of school numerous times and that Yu had modified school documents to list him as her stepfather. Yu is on her way out of town with her nicest clothes and some of her mother's money and jewelry, according to her mother. His family reported him missing two days after Amy's family filed their missing-person report.
As 45-year-old Kevin Esterly sits in a Miami jail awaiting his extradition to Lehigh County, 16-year-old Amy Yu is back in Allentown.
The age of consent in Pennsylvania is 16, according to the Pennsylvania Coalition Against Rape.
Frank Castrovinci said he saw a young Asian girl with "very long, straight hair" and a man in his 40s with glasses who boarded the plane late. She said she cried from relief upon hearing the news that her daughter was found.