Investigators said the girls gave the phone to the discipline office and that Walker was relieved of his duties and trespassed from the school the same day.
“To think that someone who works inside the school is doing that, it really kind of freaks me out,” said Oviedo High student Alani Yruretagoyena.
The school district said Walker was not an employee, but a contracted custodian with a company called AUE. The company said Walker had worked at several schools, including Lake Mary High, Lyman High and Idyllwilde Elementary.
Police said the videos found on the phone from Oviedo High spanned three days -- Nov. 7, Nov. 8 and Nov. 11.
Officers said they are also looking at a similar video found on the phone that didn’t come from Oviedo High.
Police said Walker was arrested Tuesday and charged with eight counts of video voyeurism on a person younger than 16 and one count of video voyeurism on a person older than 19.
Officers said the faces of victims were not visible in the recordings, but that detectives were able to use school security footage to identify them by their clothing.
Walker is being held at the Seminole County Jail on $90,000 bond. If he is released, he's not allowed to be around minors or on any school campus, and will also have to be tracked by a GPS monitor.