Authorities here say they can only hope for the best in the case of a missing 8-year-old Fernley girl who was abducted on Friday by a convicted sex offender.

Fernando Aguerro (search), 47, has fled to his native Mexico. He told his sister in Las Vegas he would leave Lydia Bethany-Rose Rupp (search) with the first Christian family he found to return her to her mother in Fernley. Aguerro lived with the mother.

So far, he has not made good on his promise.

Lyon County investigators believe the pair is in Tijuana, where Mexican and federal authorities continued to search for them.

"He is a predator and con man that manipulated and eyeballed a single mother," Sheriff's Capt. Jeff Page said. "Our priority is Lydia's safety, but with his background and not knowing his intentions, the reality is that we are assuming the worst and hoping for the best."

A statewide Amber Alert was issued Saturday morning, the second Lyon County abduction to be broadcast since June 23, 2004 when Walter Ball Jr., abducted his three estranged daughters after shooting their mother in the neck and beating a neighbor. One of the girls later shot and killed him when he passed out in his vehicle.

Aguerro, who goes by multiple aliases, had been living with Lydia, her mother, and her 10-year-old brother in the Villa Park modular home park since May, park manager Clyde Clemons said.

Authorities said that in the 1980s, Aguerro was convicted in Los Angeles of lewdness with a child and served one year in prison. Page said the mother was not aware of her boyfriend's criminal history.

Federal and state law mandates all sex offenders register their addresses with local law enforcement, something Page said Aguerro never did in Nevada. He said Aguerro's past was undetected until Friday's investigation.

"He appeared to be a decent guy, protective of the girl and a father figure," Page said. "Initially he didn't appear to raise a lot of suspicion. We teach our kids about stranger danger, but how do we teach them not to trust the ones they love?"

Pastor Matt McCreary, who ministered to Lydia's family for more than a decade, said he and other church members confronted the mother last week because they feared that Aguerro and Lydia were becoming "too close."

McCreary, who heads Living Faith Christian Fellowship (search) in Fernley, said Aguerro was aware the girl's mother wanted him to leave. Page said Aguerro took the girl's birth certificate and Social Security card, apparently intending to pass her off as his daughter. He also took her dog and all photographs of the girl.