although randolph parker had been suspended earlier that day, he returns later and paces outside herr. >> obviously through his anger, he wanted to take out revenge, blamed her for the problems he had been having. y 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 position himself on the other side of the hallway. according to police, harris' role was to get the assault on his cell phone camera. at one point parker even sends another student into the class to coax the teacher to come out into the hallway. >> there's no doubt mr. parker did plan the attack. they put a little bit of thought into it because they get there right at the end of the day. >> it's 2:15 and class is letting out. unbeknownst to parker and harris, the school's surveillance cameras capture the entire incident. >> through the eye of the camera you'll see the whole thing. you'll see parker get behind her door. and a