Oscar Ayala-Cornejo followed the path that leads many red-blooded Americans to law enforcement.

His family lived next to a crack house in Milwaukee, where he says he often heard gunshots and came home to find thieves had stolen the things that his father had worked hard to provide for his mother, older brother and sister.

So he got excited when two officers visited his high school to recruit police aides. The doe-eyed 15-year-old decided he wanted to become a cop, maybe make things a little better than he had it growing up.

"I wanted to change my neighborhood, to change other people's neighborhoods, so they could feel safe, you know," says Ayala, now 25. "Because I didn't feel safe."

He wanted that, it turns out, badly enough to break the law.

Though Ayala's family moved to Wisconsin in 1992 from Guadalajara, Mexico, he says he didn't realize until after he'd made up his mind to wear a badge that he was in the country illegally. He didn't know it until his father, Salvador, told him that if he wanted to be an officer, he would have to go back to Mexico and apply for citizenship, a process that can take at least 10 years.

Ayala cried and soon his father, mother and brother wept, too.

A few days later, his father found another option — one that would help Ayala get his dream job, but also would take it away and could cost him his freedom.

His father's cousin, Carmen, who lived in Chicago, would allow Ayala to take the identity of her son, Jose Morales, who was born five months after Ayala in Illinois and died of stomach cancer when he was about 7.

"That was the only option we had if we wanted to stay together," Ayala told The Associated Press recently.

Before his junior year, Ayala — calling himself Morales — switched high schools. The 16-year-old cut his hair, replaced his glasses with contacts and got braces.

In public, he called his parents aunt and uncle and his brother and sister cousins.

It wasn't easy adjusting to a new name and birthday. But the toughest part was not identifying his mami and papi in front of others.

"That really hurt," he says. "Those are my parents."

He was nervous that his true identity would be discovered when he applied to be a police aide at 17, but he had also established a work history at two clothing stores and an electronics store.

After he graduated in 2001, he entered the police aide program and stopped looking over his shoulder.

"Everybody at work, people at school, everyone I met would call me Jose so eventually that was me," he says. "Besides my family, no one else called me Oscar."

He became an officer in December 2004, about 10 months after his father died of leukemia. Eventually, he worked in the same district as his brother, Alex, a fellow officer who was born in the U.S.

And he found it rewarding.

Ayala and his partner once took a knife from a suicidal man on Christmas, he says. Another time, he found a 2-year-old boy walking alone and went door to door until he found his parents. He was helping people, and doing it by the book — except for his secret.

Ayala says he never told anyone about his true identity. But on Feb. 20, an anonymous caller informed Special Agent Russell Dykema of U.S. Immigration and Customs Enforcement that officer Jose Morales was really Oscar Ayala-Cornejo, an illegal immigrant.

Dykema spent more than two months comparing data in immigration databases and school records. He even compared yearbook photos.

Ayala was arrested May 31 by two sergeants who took him to the training academy and eventually the immigration office with shackles and handcuffs, where Dykema and another agent explained what they knew.

"I thought I was going to retire and live happily ever after, pay my taxes and all," he says. "It didn't cross my mind at all ... not until that moment."

He sat in jail for a few days, his mind racing: "Who told? Why are they doing this to me? What will happen next? What will happen to my family? How long will I be here? Will someone know I'm a cop in here? What would my father think?"

When he couldn't answer the questions, he started sobbing.

Ayala was charged with falsely representing himself to be a citizen. Two weeks later he agreed to a plea deal.

He could get a year in a federal prison when he is sentenced Monday, or he could get probation.

Assistant U.S. Attorney Mel Johnson said Ayala's position gave him access to weapons and confidential information, although there was no indication he had abused either privilege.

"When our identity systems lack integrity it's a serious issue," ICE spokesman Tim Counts said. "It's a community safety issue. It's a national security issue."

No one from the Milwaukee Police Department is commenting because Ayala is no longer employed there.

His brother likely will be out of a job soon, too.

The department fired Alex Ayala-Cornejo, a five-year veteran, in September for withholding information about his brother. He's appealing.

Oscar Ayala once wondered who the informant was and what the motives were. He didn't think he had an enemy.

Now, he accepts the consequences.

After he leaves prison, he will be permanently deported. His girlfriend of a year plans to follow him to Mexico.

"The cards that we were dealt just weren't the best ones," he said. "If I wouldn't have done this, I would still be in Mexico waiting to see if I could ever see my family."