SAN MATEO, California. – According to the San Mateo County Sheriff’s Office, a 19-year-old man is under arrest for using social media to harass teenage girls.

William Coultrip, of Pleasanton, was taken into custody last week in San Mateo County. The investigation began last month, officials said, when a teenager said she was the victim of an unknown perpetrator. They say the investigation revealed that Coultrip used social media applications such as Snapchat to have hundreds of inappropriate conversations with underage girls.

Investigators said Coultrip often drove to the victims or asked them to come to him by public transportation. Coultrip used several fake names, including “John Kelly” and “Josh Foire.”

Last Thursday, detectives worked with Pleasanton police to locate and arrest Coultrip. He is charged with sexual contact with a victim under the age of 18, assault with intent to commit a crime, meeting with a minor for lewd purposes, contact with a minor for sexual purposes and sending harmful messages to a minor.

Investigators believe there are more victims and encourage anyone with information to come forward.

Bay City News contributed to this report.