AZUSA — A 23-year-old Gladstone High School volunteer was behind bars Wednesday on suspicion of carrying on an inappropriate relationship with a 16-year-old student, officials said.

Eric Duong is also a former volunteer at West Covina High School, and worked or volunteered at El Modena High School in Orange and Tustin High School in Tustin, Azusa police Lt. Steve Hunt said in a written statement.

The West Covina resident was arrested Tuesday on suspicion of felony sex charges, the lieutenant said.

The parents of the alleged victim contacted police Tuesday to say they believed their child may be involved in an inappropriate relationship with Duong, the lieutenant said.

“The investigation revealed Eric Duong engaged in sex acts with the victim, who is a minor,” Hunt said.

Police declined to release the gender of the involved minor Wednesday.

“(Duong’s) role at Gladstone High School is not clear at this time, but it does not appear he is actually employed by the Azusa Unified School District and was an informal volunteer,” Hunt said.

At all of the four school’s Duong was known to have worked or volunteered at, he instructed extracurricular activities.

“It appears this may have been an isolated incident, but we are reaching out to ensure there are no additional victims,” Hunt said.

Anyone with information is asked to call Azusa police Detective Jerry Jarrett at 626-812-3200.

According to sheriff’s booking records, Duong was being held in lieu of $50,000 bail and was due for arraignment Thursday in Pomona Superior Court.