Bond has been set at $100,000 for 19-year-old Alex Robinson, charged with attempted sexual assault.
Harris County Sheriff's Office deputies said Robinson attacked a woman inside the Cricket store on Fry Road earlier this week.
Han An and his three children, Simon, Christian, and Hannah, were in their tae kwon do studio next door when they heard the woman's screams and came running.
"We heard the second scream, which was a horror scream," Simon remembered. "Very loud."
The An family said they went inside the wireless store and opened the door to the back room to find a man on top of the young female employee.
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Han said he had seen Robinson on a bike outside the store earlier in the day. Despite having trained in martial arts for years, the An family said they had never had to use their skills outside of the studio.
"My dad just grabbed his shirt, twisted it so he doesn't move," Simon said. "He pinned him in the corner, and that's when he started assaulting my dad by biting him and scratching him."
Han used his skills to subdue Robinson before HCSO deputies arrived and took him into custody.
Investigators said Robinson doesn't know the woman he's accused of attacking.
During his court appearance, a public defender told the court Robinson had mental health issues.
Robinson is expected to appear again in court on Friday.