It happened over the weekend at Hershey Park in west Houston.
On any nice day, Hershey Park is a popular place.
"There's always a sense of community in this park and there's a lot of kids and parents," parent Susan Nguyen said.
Even at five, Nguyen teaches daughter Zoe what she can.
"At any age, you always want to tell your child to be aware of strangers," Nguyen said.
And as they get older, and a little more independent, parents like Evelyn Davis teach in other ways.
"They both take martial arts with me. I teach martial arts so one of the things is I make sure they know their self defenses and things like that. I think it's important," she said.
And that's because danger can come on quickly.
"Yeah, very fast, very fast. You turn your head and they are gone," Davis said.
That's what precinct five deputy constables say happened on a bike trail Sunday.
An 11-year-old girl was separated from her family briefly as she rode ahead of her family. Then she stopped to get a drink of water. Investigators say a man who was sitting on a bench grabbed the handle bars of her bike and said "Let's go."
"It's really alarming," Nguyen said.
The girl was able to ride away safely.
"It might get lonely in some places where there are not many people walking around or running around," parent Anjali Jhingren said.
Now parents at the park are even more vigilant.
"I think I'm going to tell him stick to mom," Jhingren said.
Now investigators are left searching for a man in his late teens or early 20s with a dark tan. He is about 5 feet 9 inches tall, 120 pounds, with medium length, straight brown hair. He has green eyes and was wearing a gold earring in his right ear that looked like a dragon.
If you have any information on the case, contact the Harris County Precinct 5 Constable's Office at 281-463-6666.