Reporter: May 23, 2014. The sun was setting on a quiet spring night. The campus, half empty over the memorial day weekend. But the lives of those who were there would never be the same. Hours before... See More
Reporter: May 23, 2014. The sun was setting on a quiet spring night. The campus, half empty over the memorial day weekend. But the lives of those who were there would never be the same. Hours before we were having a great time. It was a nice day outside, it was sunny, you know. Reporter: After three years of meticulous planning, Elliot Rodger's deranged mind brought him to what he called "The day of retribution." The day in which I will have my revenge against humanity, against all of you. Reporter: His parents were having dinner in Los Angeles with friends. They had plans to see Elliot the next day. He was due to come on Saturday for lunch. The day after the 24th. Do you think he already knew what he was going to do? Yeah, after Reading the journals, yeah, I do. Reporter: What Elliot's journal revealed was a masterplan of carnage. I will drive down to my father's house to kill my little brother, denying him of the chance to grow up to surpass me, along with my stepmother soumaya, as she will be in the way. My father will be away on one of his business trips, so thankfully I won't have to deal with him. I was meant to have a meeting in London, and he wanted to know the dates. Why? He wanted me out of town so that he could come and murder his brother and soumaya. I think he was scared that he would hesitate, and I can understand that. Reporter: The only thing that saved his family's lives was a change in peter's schedule. My wife and jazz, my 9-year-old are still alive because of that. Reporter: What peter Rodger didn't know was that his son had already murdered three people that night. His two roommates, David Wang and James Hong and their visiting friend, George Chen. They had been brutally stabbed to death in Elliot's beachside apartment. Hours later at 9:17 P.M. Elliot e-mailed his manifesto to friends, his therapist and his parents. I will specifically target the good-looking people, and all of the couples. Reporter: Now, he was a predator in search of the rest of his prey. I'll be a god, exacting my retribution. Just for the crime of living a better life than me.ee. Elliot knocked at the door. No answer. Then got back in his car and opened fire on girls in front of alpha phee. Two of the women were dead on arrival of the deputies. One of them was very seriously injured with multiple gunshots. Reporter: At the sheriff's dispatch center, the calls poured in like rain. We have three down on the corner of Segovia. It's a black BMW. Three ambulances here. Almost simultaneously, we received notification that another individual had been shot. Response for multiple gunshot victims in front of the iv deli. At the Isla vista deli, just up the street. Reporter: Dylan fontiyas had just entered the deli. I heard the glass breaking. Just the shatter of the glass. And that's when we all started scrambling for our life. Reporter: When Christopher Martinez came in for a sandwich, he was cut down in a hail of gunfire. Shots fired. Shots fired. I had just turned. I saw him fall. I kind of like tucked my hand over my head and turned down and ducked behind the counter. We sat there, and watched this kid bleed to death. He was no less than two feet away from me. Reporter: But the rampage was far from over. The deadly shooting in Isla vista with multiple victims. Three people have been shot. All of a sudden sirens start going, ambulances start going. Multiple places, multiple people. The death toll could be climbing. He went up to the top of the loop firing. He shot three more victims. I'll take to the streets of Isla vista and slay every single person I see there. He then confronted another young woman, and pointed his gun at her. Reporter: At first, Sierra Schwartz thought the gun was a toy. He shot and I felt like -- I just felt the wind like pass right by my face and I was like what the -- so I turned around and I started like walking really fast the other way. Reporter: The deadly BMW was swerving erratically through the streets. People were like, "They're shooting! They're shooting!" Reporter: Drawing gunfire from officers. He fired rounds at the deputy sheriff. And the deputy sheriff replied with one round of gunfire. About 8 to 12 shots just super-fast were fired what sounded like directly, directly below my balcony. Reporter: That black BMW plowed it's way over pedestrians. Some guy ran into our house bleeding everywhere. Said he got run over by a car. Reporter: There was carnage and chaos everywhere. As many as seven victims taken to the hospital. Reporter: But after deputies fired on him for the second time, Elliot's car spun out of control. Three of the deputies returned fire, and struck the vehicle. Reporter: Witnesses say they heard a single shot from inside the car. The long night's journey into terror had finally come to a close. Did Elliot kill himself, or did the police kill him? What I gather is that he was shot in the hip, and then he took his own life. How did you learn that your son was the shooter? The sheriff came. I'll remember this forever the rest of my life. The way, you know, he just looked me in the eye, and he said, "We've found a deceased person, and we found a license in his pocket that fits your son's description." And I went -- oh. I did not know that he was the perpetrator. I thought he was a victim. You did not know then? I thought he was a victim. Reporter: A search of Elliot's BMW revealed an arsenal. Three semiautomatic weapons and 400 bullets. Elliot had been ready for armageddon. Who would have thought my life will turn out this way? I didn't start this war, but I will finish it by striking back. Finally, at long last, I can show the world my true worth. Reporter: In the end, seven people lost their lives, 13 were wounded. It took less than eight minutes to transform one square mile of suburbia into a killing field. I've never actually, literally looked in the face of the devil, you know? Which is terrifying. Reporter: In life, Elliot Rodger had passed almost invisible to everyone around him. Who would have known to stop the quiet boy hiding a monster within? He lived, like, a 20-second walk from my house and I've never seen the kid in my life. He went to the same school, we ate at all the same places, but I -- you know, he's just another
This transcript has been automatically generated and may not be 100% accurate.