HOUSTON -- Spring Branch Independent School District students are on the lookout for a man who police said exposed himself to three different girls at three different campuses in the district, KPRC Local 2 reported Monday.

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Slideshow: Spring Branch ISD Sexual Predator

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With the man, believed to be in his 20s, on the loose, Spring Branch ISD Police Chief Chuck Brawner said he fears what the man may do next.

The man managed to get past a school's office and into a courtyard, officials said.

"This being a young individual, he blended in with population there," said Brawer

All three indecent exposures allegedly happened on April 23.

The man first approached an 18-year-old girl at Stratford High School, police said.

Police said the man called the girl over to his red Jeep to ask for directions. When she got close to the vehicle, the man was naked from the waist down and asked for a sexual favor, officials said.

The girl walked back toward the school.

Investigators said the man then drove to Memorial High School, where he walked onto campus and exposed himself to a 15-year-old girl while she was waiting for a ride.

Police said the man asked the teenager for a sexual favor several times before she walked back into the building.

Minutes later, he did the same thing to a 13-year-old girl just around the corner at Spring Branch Middle School, officials said.

Students and parents said they hope the man is caught soon.

Memorial High School senior Lindsey Mueller said, "It's really scary. A lot of girls don't want to travel alone anymore."

Parent Barbara Betancourt told her kids, "They're told to stay in groups and leave campus as soon as school is over."

The man was described as black, in his early 20s, 5 feet 9 inches to 6 feet tall with a lean, muscular build. He was last seen wearing a white shirt with blue stripes, blue or black mesh shorts, white athletic shoes and a white baseball cap.

Anyone with information about the man is asked to call Crime Stoppers at 713-222-TIPS.