WHITTIER, Calif. (KABC) -- A Whittier school bus driver has been charged in the death of a student with autism who was left in the vehicle on a hot day, the Los Angeles County District Attorney's Office announced Friday.Armando Ramirez, 37, of Rialto, was charged with one felony count of dependent adult abuse resulting in death.Police said 19-year-old Paul Lee was found dead on a parked school bus floor at a bus yard in Whittier on Sept. 11, 2015.Lee was a student at Sierra Adult School who could not verbally communicate and needed special care, officials stated.Prosecutors said all of the windows on the bus were closed and the temperature that day was near 90 degrees.Officials said Ramirez was a substitute driver for Lee's bus that day and stated he was working a split shift.According to prosecutors, Ramirez did not check the bus after ending his morning shift and returned to the bus yard to fill out paperwork before heading home.When he returned for his second shift of the day, prosecutors said Ramirez was notified Lee was missing.That's when prosecutors said Ramirez checked the bus where he found Lee unresponsive and called for help.Ramirez posted bond on Friday and was released. He was scheduled to be arraigned in Los Angeles County Superior Court on April 25.If convicted as charged, officials stated Ramirez faces a maximum of nine years in state prison.