HOUSTON, Texas (KTRK) -- Inside the Wu Training Studio off Richmond and Hillcroft, investigators say the family-owned business was hiding a dark secret.
One of the instructors, known as Coach Ivan, is a convicted sex offender who never registered as one and changed his name.
"Kind of just been living under the radar, under an alias, and no one really knowing the truth of his nature or what he had done," said Robert Ezzell, a former employee at the studio.
The U.S. Marshal's office said "Ivan's" real name is Felipe Ramon Corona. In 2011, he was convicted of sexual assault of a child in McAllen, Texas.
The victim was a 16-year-old girl who investigators say Corona met while working at a martial arts studio there.
After his conviction, he never registered as a sex offender and instead, claimed he moved to Mexico.
Nearly a decade later, the U.S. Marshals were tipped off by someone who said they saw Corona's photo on a social media post for the studio.
Investigators discovered Corona was working at three family-owned businesses in southwest Houston: Spartan T-shirts, Wu Fighting World and Wu Training Studio.
Ezzell said Corona was working with and around children and teenagers.
"Even my own girlfriend's daughter for quite a while," said Ezzell, who worked at the business with Corona and his brother for three and a half years.
Ezzell said he quit the Wu Training Studio shortly after the U.S. Marshals approached him last week.
Corona was arrested Tuesday.
"It really hurt to know the fact that not only did Felipe, or as we know him as Ivan, did these things but also that his family covered it up, and called him by the name Ivan and allowed him to be around kids, teenagers, being the sex offender that he was," said Ezzell.
The jiu-jitsu instructor says he has been working to inform all the families and clients.
"I do worry that, you know, there may have been an opportunity for him to hurt another child, but I'm pretty certain that the kids I was with ... he never had a chance to be one-on-one with them," said Ezzell. "The really sick part about it, and the reason the U.S. Marshals told me that they really wanted to get him out of that atmosphere, because it was the exact same thing he did about 10 years ago prior. You know, he was in a martial arts studio in McAllen, Texas, and now he's in Houston, Texas, in a martial arts studio in the same exact environment."
He urges families to request background checks on anyone who works closely with your child.
Police are asking any victims to speak up and call the Houston Police Department.
For updates on this report, follow ABC13 reporter Shelley Childers on Facebook, Twitter and Instagram.
Houston martial arts instructor arrested for failing to register as sex offender
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