The pickup then ran into a ditch and Murray pulled Sanchez out of the pickup and shot him again, Palmer wrote in the affidavit.
Murray got a ride from a passing car after covering Sanchez's body up with leaves and sticks, according to the affidavit, and Murray said he had no remorse for the killing.
East Central spokeswoman Amy Ford confirmed Sanchez and Murray both were freshmen at the school.
“Our thoughts and prayers are with the family and friends at this painful time,” Ford said.
Sanchez was a 2012 graduate of Stuart High School, according to his Facebook page.