A Miami Police officer was arrested Wednesday on charges of armed sexual battery by a law enforcement officer and armed kidnapping, authorities said.

Luis Hernandez, 27, a seven-year member of the police department, was arrested by internal affairs detectives after DNA evidence backed up a woman's claims he kidnapped and sexually battered her in November 2011, police said.

"The findings were enough to have a Miami-Dade County judge sign an arrest warrant and charge Officer Luis Hernandez with sexual battery by a law enforcement officer and armed kidnapping," Miami Police spokeswoman Officer Kenia Reyes said.

The charges stem from an early morning alleged attack by Hernandez on Nov. 26, 2011. That day, he was called in to relieve an officer going off-duty by transporting a 44-year-old woman to to the Miami-Dade County Jail. She had just been arrested after an earlier bar fight, police said.

'I'm going to help you'

Hernandez picked up the victim from a colleague at police headquarters just after one o'clock that morning. Soon after, she said, he drove her to a parking lot off the 2500 block of Northwest 2nd Avenue. She recalled that Hernandez told her, "I'm going to help you," police said.

The victim told police internal affairs investigators that Hernandez gave her some gauze and told her to clean up her face. With her shirt torn from the fight hours earlier, she recalled Hernandez poured a liquid onto a scratch on her breast. Then, she said, Hernandez lifted her shirt, and began fondling her.

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Police documents note the victim told investigators that Hernandez, dressed in police uniform, removed his duty belt and exposed himself. According to the victim, the officer then told her to "get down," a demand, she believed, for oral sex.

The victim refused, and she claimed Hernandez began fondling her private parts. According to police, she said he then ordered her to turn around, and she begged him to stop.

After the encounter, the victim said she was handed off to a detention officer, but because of her wounds, that officer asked Hernandez to come with him and the victim to jail. While being processed, the victim, who is a Spanish-speaking undocumented immigrant, felt comfortable sharing the story that would launch the investigation, police said.

Within months, DNA evidence linked Hernandez to the crime, they said.

Mayor Tomas Regalado told NBC 6 the investigation and arrest proves the city demands the best of its officers.

"To me, this is not a scandal, this is a clean up of the department," he said.

Hernandez is being held without bond, online Miami-Dade Corrections records said. It was not known if he has an attorney.