The piercing scream, like a sound from a horror film, triggered taekwondo instructor Simon An to draw on his years of martial arts training.

Around 4 p.m. Tuesday, shortly after the doors of his family-owned and -operated studio in Texas opened for evening classes, An and his father, his mother, his older sister and his younger brother heard shrieks coming from a neighboring business.

The family of five, each with a fourth-degree black belt, run the Yong-in Taekwondo studio in Katy, outside Houston. They initially ignored the sounds, assuming they came from employees playing around in their break room. But then a piercing “final scream” prompted the family into action, A said.

His family ran to the store and opened a door. There they found a man on top of a young woman with his hands “in [in]appropriate places” as she attempted to fend him off, A said.

An’s father, Hong, yanked the attacker away by his shirt and pinned him to the ground. An’s sister, Hannah, grabbed the girl and rushed her out of the room while An and his brother helped subdue the attacker.