LONG BEACH, Calif. (KABC) -- Police are asking for the public's help to track down a man wanted for exposing himself three separate times near Woodrow Wilson High School in Long Beach.The incidents occurred between Feb. 6 and May 14, Long Beach police said.The first incident occurred on Feb. 6 at around 6:45 a.m. near 7th Street and Mira Mar Avenue. A woman was walking in the area when she saw a man between 20 and 25 years old masturbating inside a silver vehicle, police said.The second incident occurred on May 1 around 6 p.m. near 10th Street and Ximeno Avenue. A female juvenile was walking in the area when she saw a man sitting in a gray vehicle masturbating, authorities said.The third incident occurred on May 9 around 3:20 p.m. near 11th Street and Molino Avenue. A female juvenile was walking home from school when she spotted a man around 30 years old driving a silver vehicle. Investigators said he followed the girl and then exposed himself.Police have released a sketch of the man and photos of the suspect's car in hopes that someone will be able to identify him. He's described as a white man between 20 and 40 years old, with an average-to-thin build and short, black hair.Parents in the area said they're very concerned over the crimes happening so close to campus."I teach her different things when she walks home -- things to do, things to say in an emergency case..." said parent Kelly Brooks.If you have any relevant information about this case, you're urged to contact Sex Crimes Detective James Smigla at (562) 570-7368. You can submit anonymous tips by calling L.A. Crime Stoppers at 1-800-222-TIPS (8477).