A police officer has agreed to plead guilty to falsely claiming to be a U.S. citizen for taking his dead cousin's identity as a teenager, according to the U.S. attorney's office.

A plea agreement released last week says prosecutors will recommend a sentence of six to 12 months for Oscar Ayala-Cornejo, 24. The maximum sentence is three years in prison and a $250,000 fine.

Ayala-Cornejo also agreed to be deported after his prison sentence and resign from the Milwaukee police department, Assistant U.S. Attorney Mel Johnson said. The officer, who authorities said was not involved in any major cases, had been taken off the department's payroll earlier this month.

In February, a U.S. Department of Homeland Security agent received an anonymous call from someone reporting Ayala-Cornejo was an illegal immigrant but was using the identity of his dead cousin, the complaint says.

Investigators compared Ayala-Cornejo's driver's license to yearbook photos from two high schools he attended as two different identities, the complaint said. Relatives also admitted Ayala-Cornejo took the identity of Ayala-Cornejo's cousin Jose Morales, who was born in Chicago about seven months before Ayala-Cornejo.

Ayala-Cornejo's mother, Maria, told authorities her now-dead husband helped arrange the identity theft with relatives in Chicago, according to the complaint.

Jose Morales died of cancer, Morales' brother, Jamie, told authorities. Jamie Morales said his father volunteered Jose's identity when he died, the complaint said.

Ayala-Cornejo moved from Mexico to the U.S. around 1992, Johnson said.

He started using Morales' identity in 1999 when he changed high schools in Milwaukee, according to the complaint.

Johnson said Ayala-Cornejo could have gone through the administrative process, but instead took the illegal method.

"That was just perceived as the easy way to do it but it turned out to be a bad decision," Johnson said.

No sentencing date has been set.

Police say Ayala-Cornejo's brother, Alexander Ayala, who is also a Milwaukee police officer but is a U.S. citizen, has been assigned to administrative duty.

Messages left at Ayala-Cornejo's home and for his attorney, Michael Steinle, were not returned Monday.

Chief Deputy District Attorney Jon Reddin said Ayala-Cornejo was involved in 23 cases since he's been on the force; of those the defendant pleaded guilty, the charges were dismissed or Ayala-Cornejo wasn't a crucial witness, Reddin said.

"He doesn't appear to be a terribly active officer," Reddin said Monday. "We're fortunate he wasn't involved in any major cases."