Steve Paul Popper, 47, a special education teacher at Bemis Elementary School, is behind bars facing eight felony charges, including forcible lewd acts with children under 14.
For parents, the allegations are both shocking and infuriating.
"We're mad and we're concerned, because we're like what if something happened to our kids because I have multiple kids that go here," said parent Taufau Lauem of Rialto.
Earlier this month, investigators with the San Bernardino County Sheriff's Department were tipped off by an internet service provider about Popper's online activity after he allegedly downloaded child sexual assault materials.
According to District Attorney Jason Anderson, detectives acted quickly because of the potential danger to children.
In a statement, Anderson said:
"San Bernardino County Sheriff's Internet Crimes Detectives acted swiftly due to the potential harm to children. Their investigative efforts revealed that the alleged crimes went beyond possession and involved physical child sexual assault."
Authorities say at least four children under the age of 14 have been identified as victims, and investigators believe there could be more.
For some parents, the allegations strike at the heart of their fears about trust and safety in schools.
"Just the decay of our society. It's sad, it's really sad," said Lena, a Rialto resident who homeschools her son. "Anybody that would hurt children, it just makes me want to cry, honestly, it makes me sick."
Lena said she decided to homeschool her son in part to feel safer about his education.
"I know it's tough to homeschool. There's a lot of pressure, but it makes me feel like, who would love him more than me?" she said.
In a statement to Eyewitness News, the Rialto Unified School District said Popper was placed on immediate administrative leave after law enforcement notified the district. Officials said they also accepted his resignation shortly after.
"The District is deeply disturbed by these serious allegations and will always continue to ensure the safety of students as its main priority," said RUSD spokesperson, Syeda Jafri.
Popper was arrested at his home on Wednesday and initially posted bail, but was re-arrested the following day on a no-bail warrant, according to investigators. He is due in court for his arraignment on November 3rd.