. >> reporter: doug estle was the principal at murphy high school. rapport with his students. but one afternoon on may 18th, 2007, one of those students commits a violent and senseless crime. >> a student was being placed under a suspension from a teacher's classroom. >> 16-year-old randolph parker, seen here in the blue shirt, khaki colored pants, is the problem student in 61-year-old melissa's ninth grade english class. she's giving a party that afternoon in her classroom for an exchange student who's returning home. although randolph parker had been suspended earlier that day, he returns later and paces outside her door. >> obviously through his anger, he wanted to take out revenge, blamed her for the problems he had been having. so he set up a plan, obviously, to come back at the end of the day to attack her or to hit her. >> as this last period progresses, you can see randolph parker, walking up and down the hallway, waiting for the class to end. he puts on a red bandana over his face and signals to his cohort, 17-year-old dominic harris, to pos