By Tony Lopez

SACRAMENTO (CBS13) – A Sacramento personal trainer and kickboxing instructor has been arrested on charges that he sexually assaulted a female teenage student of his.

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Sacramento County Sheriff’s Department detectives arrested Fernando Santos, 35, on Wednesday.

Fernando Santos

Santos was booked into the Sacramento County Main Jail on charges of oral copulation and unlawful sexual intercourse with the 17-year-old girl. Santos posted bail and was released from custody Thursday, the sheriff’s department said.

The alleged victim is believed to have been assaulted by Santos on several occasions from April 2011 until this January. The victim ultimately reported the alleged assaults, and detectives arrested Santos at his residence based on the victim’s claims and further investigation.

Reaction to the news at the Muay Thai Lau Kickboxing Academy was that of shock and sadness.

“I’m shocked that this happened,” said Vinnie Vantonkum, who used to train with Santos.

But the gym was determined to point out that Santos is not an employee of this kickboxing academy on Howe Avenue in the Arden-Arcade area of Sacramento.

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“Our affiliation with Fernando is he rented space from us,” said Vantonkum. “He’s renting space from Moy Tai Lau to do his personal training classes.”

When Santos didn’t show up to teach a private class earlier Thursday, management wondered what had happened. Now they know.

The 35-year-old instructor – who calls his business “Team Santos” – was well known for his all-female class on Sundays.

Investigators aren’t saying if his alleged victim was enrolled in that particular class. But they do say the 17-year-old is one of Santos’ former students.

While his legal fight is just beginning, the place where he rented out space is fighting to clear its reputation.

“We have our own regular kids classes and adult classes that’s totally separate from Fernando … and I just want to make that clear to everyone,” Vantonkum said.

Due to the nature of Santos’ occupation and the fact that he had numerous students, detectives say they believe there may be additional victims of similar crimes.

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Anyone who had inappropriate contact with Santos or has knowledge of unlawful activity on Santos’ part is asked to call Detective Kelly Clark of the sheriff’s Sex Assaults Bureau at (916) 874-5070.