The Agony of a Dad Whose Son Became a Mass Killer

It was in the parking lot of a Home Depot in Isla Vista, Calif., that Peter Rodger would learn that his 22-year-old son Elliot was dead.

"I'll remember this forever the rest of my life," Rodger said. "The way [the sheriff] 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.'"

Elliot's mother, Li Chin Rodger, and Peter's current wife, Soumaya Akaaboune, both protested to the police. "No, no, no, no, he's not dead," they pleaded.

"Can somebody clarify this to me?" Peter Rodger asked in the confusion.

The sheriff gave the same cold answer. "We've found a deceased person, and we found a license in his pocket that fits your son's description." It was that moment Peter Rodger realized that his son was actually gone.

Watch a special edition of "20/20," "The Secret Life of Elliot Rodger," Friday, June 27 at 10 p.m. ET

What he didn't know yet was that his son was a mass murderer, that Elliot had used knives, handguns and his car to murder six people and injure 13 near the UC-Santa Barbara campus before taking his own life. The carnage caused by his son transfixed that nation on May 24 as his fury left a trail of blood through the campus town.

Read Peter Rodger's Open Letter: "We Have to Try and Stop This"

How to Spot Signs of Mental Illness and Ask for Help

Earlier that evening, Peter Rodger had been enjoying dinner with friends at his home a hundred miles south in Los Angeles. He had received an e-mail from his son. Elliot's mother received the same email which contained a menacing 137-page diary addressed to his parents, life coach, and others entitled "My Twisted World."

Li Chin had Googled her son's name and found something even more chilling - a YouTube video called "Elliot Rodger's Retribution." It showed her son sitting in the driver's seat of his black BMW - a car which he would turn into a deadly weapon - spewing a hate-filled, sexist tirade.

Before Peter Rodger could read the e-mail he received a desperate phone call from Chin. "You've got to go on YouTube," she implored, sending him the link.

"I just went to the YouTube page and saw, the retribution video," he said with a sigh. Watching his son say such terrible things, Peter Rodger said he remembers a wave of darkness washing over him. "A really dark force of horrible energy hit me."

That was the beginning of a nightmare that won't end for Peter Rodger as he continually relives the moments of his son's life, from the happy days when Elliot was a laughing little boy to his increasingly dark world. He recalls with a twinge of regret the what-could-have-been moment when Elliot's alarmed mother called police on her son, but they left after Elliot convinced them that his online rantings were harmless. At that point Elliot had already purchased three guns and had been practicing at a firing range in preparation for his "retribution."

Peter Rodger said he does not blame the police, but would like to see the law changed so that gun checks are required on these types of calls. "If they did do a gun check, they would know that Elliot had bought three automatic weapons. They would have the right to seize him for 24 hours, and his whole scheme would've been over and thwarted," he said in an exclusive interview with ABC's Barbara Walters.

Elliot Rodger's Father Relives Santa Barbara AttacksOn the awful night of May 24, Peter Rodger, his wife, and Elliot's mother all rushed to their cars, starting a frantic 100-mile sprint to Elliot's apartment in Isla Vista, worried for their son's safety and his life.

"I didn't know what he was doing," his father said. "I just wanted to go and find him...and talk to him, do something. You know, hold him. You know, talk reason."

Closing in on Isla Vista in their cars, nearing Elliot's apartment, they began reading on their phones about an incident involving a black BMW and reports of an active shooter on the loose at UC-Santa Barbara.

The frantic dad kept hitting redial on his phone trying to get through to his son. "We were driving up there not knowing what to do," he said.

Police stopped them as they got close to Elliot's neighborhood. "You can't go to Isla Vista. It's closed off because of a terrible incident," they were told. Police directed them to wait in the parking lot of a nearby Home Depot for details.

Although Peter Rodger had watched his son's video that night, it was three weeks before he could bring himself to read his son's manifesto. The document was an extension of what Elliot had declared on YouTube. He detailed his childhood, family problems, his inability to get a girlfriend, and his hatred of women, ethnic minorities and interracial couples. And it contained his plans for a massacre.

Peter knew that his son had been writing, though Elliot had refused to share what he was writing about. On a hike with his son sometime before the killing spree, Peter Rodger asked, "'Can I please read it? Can you please just send it to me?' And he said, 'Oh, no, no, no. I'll send it to you soon enough.' I had no idea it was this."

His father said he never believed that his son would have done something like this, despite the years of therapy.

"Elliot was far from evil. Something happened to him. He was the most beautiful, kind, sweetheart of a boy. And something happened to him," Peter Rodger said. "He was adorable. And he would laugh so much that sometimes we were worried he would choke," he told Walters.

Elliot Rodger was born in London to Peter Rodger and Li Chin, a Malaysian-born nurse who had worked as a unit nurse on the set of "Indiana Jones and the Last Crusade." Peter also worked in film, directing television commercials and working on the hit film "Hunger Games."

At the age of 5, Peter, Chin, Elliot and his little sister Georgia moved back to California. Those were the good years. "It was really wondrous, those first four, five years of his life. It was wondrous. He was a really adorable, cute little boy," Peter Rodger said.

When Elliot was 7, Peter and Chin divorced. A year later, Peter remarried, this time to Soumaya Akaaboune, a Moroccan actress who had appeared in the Hollywood blockbuster "Green Zone."

It was also the year Elliot began his long journey with therapy.

Elliot Rodger's Rage Began Long Before Santa Barbara ShootingElliot had had problems, "but they weren't things that I would consider overly worrisome -- or that he would ever be a threat to himself or he would be a threat to other people," his father said. Like a lot of kids, he wanted to be part of the cool crowd but had trouble fitting in. His parents moved him from school to school, trying to find a place where Elliot could succeed.

His father said he had very few friends in elementary school. He was quiet and shy. He also had "a certain OCD" about him, always putting his plate in the same place at the dinner table, always wearing the same clothes. There was a suggestion that Elliot might have had Asperger's syndrome, though he was never formally diagnosed.

Elliot said in his journal that his rage began to build even as a youngster as the son of a Hollywood insider with a front row seat to the entertainment industry's most powerful and glamorous.

"My little 9-year-old self realized that there were hierarchies, that some people were better than others. Jealousy and envy...those are two feelings that would dominate my entire life and bring me immense pain," Elliot wrote.

But Elliot hid that pain well, his father claims.

"If he were sitting here right now, you would think, 'What a polite boy he was,'" Peter Rodger said. "But yet, he had this thing going on inside of him."

Peter Rodger said he never had an inkling that his son harbored a lethal rage inside him.

"There's no way I thought that this boy could hurt a flea. He'd never, ever been violent or showed any violent tendencies ever, ever," he said.

"I think that his mind was taken over by a disease," his father has concluded.

The lonely young boy had become an introverted teenager. By the age of 13, Elliot had walled himself into the fictional cyberworld of "World of Warcraft." His constant companions were the heroes and villains of the online fantasy game.

In high school, Elliot was bullied, though his father said Elliot would never talk about it with him. There were incidents when food was thrown at him, incidents when he was pushed into lockers. "I was an innocent, scared little boy trapped in a jungle full of malicious predators, and I was shown no mercy," he later wrote in his diary.

He would leave two high schools before landing at the tiny 100-student Independence High.

For all the things that Elliot had - the Black BMW, the designer sunglasses - there was one thing that always eluded him: a girlfriend. And that became his obsession until the very end. "I mean look at me, I'm gorgeous. But you girls don't see it. I don't understand why you're so repulsed by me," Elliot stated in his retribution video before his killing spree.

Elliot Rodger Was Tormented by His Inability Find a GirlfriendSex became an obsession and an agony for Elliot.

"Finding out about sex is one of the things that truly destroyed my entire life. Sex, the very word fills me with hate," Elliot would write in his journal. "I would always covet it, I would always fantasize about it. But I would never get it."

Peter Rodger said he tried to talk about this issue with his son, but chalked Elliot's nervousness about girls to normal teenage jitters. "Of course you're going to find a girlfriend," Peter Rodger would say. "Of course you're going to fall in love. Of course you can have children. Elliot, there's no rush."

"I put it down to just straight youthful jealousy. I didn't think that he was harboring lusts of terrible deeds in his head. I didn't think that he had a plan of revenge, or all of the stuff that came out," he told Barbara Walters.

By the time Elliot reached his 18th birthday, the shy young boy had vanished, leaving behind only resentment and anger. Too terrified to approach young women, it was easier to hate them.

The campus of the University of California at Santa Barbara sits right along the Pacific Ocean. The skies are blue and clear more days of the year here than not, and Elliot's parents thought the sunshine and college life would help their introverted son grow up. Elliot attended the nearby Santa Barbara City College, although he had stopped taking classes in early 2012.

"I thought that by putting him out there and giving him independence and integrating him into a normal society would very quickly help develop the skills that I thought was lacking in him," his father said.

But it was at college that Elliot would begin planning his day of retribution. "It was only when I first moved to Santa Barbara that I started considering the possibility of having to carry out a violent act of revenge, as the final solution to dealing with all the injustices I've had to face at the hands of women and society."

His fury towards women drew him to misogynistic websites. In one online forum he wrote, "start envisioning a world where women fear you."

Elliot Rodger's Father Says He Was 'Such an Incredible Liar"When Elliot sent the websites to his father, Peter Rodger angrily called his son. "Elliot, why are you going on these websites?" he recalled saying. "This is negative, this is-- evil kind of-- And you shouldn't go on there." But the father's outrage failed to work. He failed to realize the depths of Elliot's hatred of women.

The young man became obsessed with losing his virginity. Peter tried reasoning with his son on this, too: "There is no shame at all in not losing your virginity at a later age. Some people never do. Some people go into the church and choose chastity."

Elliot's life had become a volatile mixture of desire and denial, and that tension reached a boiling point at a party last summer. He wrote that he had decided to give women once last chance to help him lose his virginity before he turned 22. When the girls at the party ignored him, he grew angry, climbed onto a 10-foot ledge and pretended to shoot party goers with an imaginary gun.

When Elliot tried pushing several women off the ledge, a group of men intervened and shoved him off instead, resulting in a broken ankle.

Elliot told his father a different story. When Peter came to pick him up, Elliot claimed he was the victim, bullied, called a faggot, and beaten up. He told the police the same story, but they dropped the case after finding out Elliot might have been the aggressor.

"He was such a good liar," his dad said. "He was such an incredible liar."

Though Elliot had seen many therapists, he was never formally diagnosed with a mental illness. And with no official history of mental illness, he was able to legally purchase three handguns to use in his attack. Three, he said, in case two of them malfunctioned.

He went to a firing range to practice. "As I fired my first few rounds, I felt so sick to my stomach," Elliot would later write. "There I was, practicing shooting with real guns because I had a plan to carry out a massacre. Why did things have to be this way?"

Elliot had launched his plan for "retribution day."

After not hearing from her son for a couple of days in April, Elliot's mother Li Chen became nervous. Intuitively, Peter Rodger said, she began sniffing around on the internet to see if there had been an accident. What she found was Elliot's YouTube account.

Elliot had been uploading bizarre videos to YouTube, although none contained a specific threat. Knowing that Elliot would never consent to a "mental assessment," Chin called the police. Six officers showed up at Elliot's door.

"Elliot was a very, very polite, kind, well-spoken, well-dressed individual," his father said. "And he managed to say, 'You've got nothing to worry about.'" The police left without taking any action or running a gun check.

As the police left, a wave of relief passed over Elliot. In just a few weeks, his day of retribution would arrive.

On that day in May, that Memorial Day weekend, Elliot Rodger would kill seven people including himself, wounding 13 others.

"I don't understand it. I can't wrap my head around it," said Peter Rodger. "It will haunt me, haunt me for the rest of my life."

Elliot's mother has declined to discuss her son or the tragedy of last May.

"I feel the world's attention should be focused on the victims' loved ones and remembering the beautiful lives that were so tragically lost," she said in a statement to ABC News.