When Simon An and his family heard screaming from a store next door to their family taekwondo studio on Wednesday, they knew they had to find out what was happening.

The family of five, each with a fourth-degree black belt, run the Yong-in Taekwondo dojo in Katy, outside Houston.

The incident happened round 4 p.m. shortly after the doors of the studio opened for evening classes.

They were returning from their lunch break and were parking when his An’s father heard a “loud scream” as he exited his car.

They initially ignored the sounds, assuming they came from employees playing around in their break room.

Then the whole family heard “a second scream, and it was loud. Very loud.” “I would describe it as a horror scream.” An said.

20 year old  An and his family immediately went to the Cricket Wireless store next door.

He heard another scream as he opened the door and rushed to the employees’ room in the back, where he found “a man on top of the woman with his hand over her mouth,” An said.

“It just happened so sudden,” said An, who has been practicing taekwondo for 16 years. “It was all self-defense

“Our first instinct was to save the girl,” An said. “We didn’t know what he was going to do to her.”

“My dad just pulled him off and pinned him in the corner of the building,” An described.

The intruder was trying to run away — scratching, biting, anything he could do.”

But An’s dad, a taekwondo grand master, held down the attacker for 10 minutes until law enforcement arrived, he said.

“My dad is strong. He expected us to protect him,” An said. “He had a lot of trust in us.”

His father sustained some scratches and bites during the scuffle but is altogether “fine,” An added.

In an interview An’s sister, 22-year-old Hannah An, said she and her mother took the alleged victim to their training center to make “sure that she’s OK, because she needed that after that experience.”

The pair’s father, Han An, said he was grateful to have been in the right place at the right time and looks forward to returning to classes.

“My life is taekwondo,” he said. “I’m very proud of my family.”

The Harris County Sheriff lauded the An family as “good samaritans”, thanked them for their “quick action in protecting others” and credited them with saving the young woman from a sexual assault.

“By utilizing their training and discipline, they managed to stop the assault and hold him,” Sheriff Ed Gonzalez said in a series of posts on X.

“Thank you to the Yong-In dojo for your quick action in protecting others,” Gonzalez wrote.

Alex Robinson, 19, was charged with attempted sexual assault in connection with the case, according to court documents.

Robinson is accused of taking the victim to a different location, “causing bodily injury by choking,” “touching her breast,” and ordering the victim to take off her clothes.

Robinson’s bail was set at $100,000.