The student, who had autism, became violent and was restrained by school workers because of the potential for injury to others, the El Dorado County Sheriff's Office said in a statement. The boy, who has not been identified, became unresponsive and a teacher began CPR, the statement said. There were no details given about what prompted the student's behavior or how he was restrained.The boy was sent from Guiding Hands School in El Dorado Hills to Mercy Hospital of Folsom then UC Davis Medical Center in Sacramento, where he died on Friday. "At this time, there appears to be no evidence of foul play or criminal intent," the sheriff's office statement said. The investigation is ongoing, Sgt. Anthony Prencipe said. "We're putting all the resources into it to make sure that we understand fully what actually happened to get to the bottom of it and just to find the truth," he told CNN affiliate KTXL.Guiding Hands School said staff members used "a nationally recognized behavior management protocol." School staff undergo annual training on de-escalating a situation, said a source with direct knowledge of school policy. The last resort is to put a student in a "neutral position," the official said.The boy was 6 feet tall and 280 pounds, the sheriff's office statement said. The school's website says it was founded in 1993. Some students have physical and behavioral issues, the source said. The school issued a statement, saying, "It is with heavy hearts that we share the very difficult news that a beloved member of our school community has passed away. Out of respect for the family, and the ongoing investigation, we are unable to share full details at this time."