Elliot Rodger's father: 'This is the American horror story'

The father of Elliot Rodger spoke to ABC News about his son's murder rampage in an exclusive interview to be broadcast on Friday

A YouTube video featuring Elliot Rodger where he speaks of his "retribution" (AP)

The father of British-born Elliot Rodger has spoken to the American media for the first time since his son killed six people and wounded 13 more in a rampage in late May.

Peter Rodger told ABC News' acclaimed anchor Barbara Walters, "Every night I go to sleep, I wake up and I think of those young men and young women that have died and who are injured and who were terrorised.

"My son did that. My son caused so much pain and suffering for so many families."

Rodger is a Hollywood movie director who worked on The Hunger Games. He said that he and his wife did not harbour any suspicions that their 22-year-old son would commit such a dreadful crime.

"There's no way I thought that this boy could hurt a flea... We didn't see this coming at all," Rodger said.

"This is the American horror story, or the world's horror story, is when you have somebody who on the outside is one thing, and on the inside is something completely different. And you don't see it."

On the night of May 23, Rodger's son Elliot began his rampage by fatally stabbing his two roommates and a visiting friend in an apartment near the University of California, Santa Barbara campus.

He then drove through the Isla Vista neighbourhood, randomly shooting at people and ramming his BMW into students. Following a gunfight with police, he shot himself.

Prior to his killing spree, Rodger uploaded a video to YouTube entitled "Elliot Rodger's Retribution" and sent a 141-page document to family and friends detailing how he planned to kill his stepmother and six-year-old brother as part of his "Day of Retribution". Elliot said he feared his brother would grow up to be more popular with women than he was.

Both of Rodger's parents tried to stop their son going on the rampage minutes after receiving the message but they heard the news of his killings on the radio as they raced to Santa Barbara.

“When you go to sleep normally, you have a nightmare and you wake up and, ‘Oh, everything's OK,’” Rodger's father told ABC News' Walters.

“Now I go to sleep, I might have a nice dream. And then I wake up and it's, slowly, the truth of what happened dawns on me. And you know, that is that my son was a mass murderer.”

Warning: Some viewers may find the following video disturbing

Rodger was found dead in his black BMW with a gunshot wound and three 9mm semi-automatic guns and more than 400 rounds of unused ammunition.