(CNN) -- The killer's parents won't talk about him.
That at least is what their friend told CNN on Thursday.
Their thoughts are on the other six victims of Friday's killing spree in Santa Barbara, the friend said.
Elliot Rodger, who fatally stabbed three people and shot three others, himself was found dead with a gunshot wound to his head after crashing his black BMW.
"We are crying in pain for the victims and their families. It breaks our hearts on a level we didn't think possible," Rodger's family said in a statement read by a family friend on "New Day."
"The feeling of knowing that it was our son's actions that caused the tragedy can only be described as hell on Earth."
In a 137-page document, not to mention videos and musings on social media, 22-year-old Rodger hinted that years of rejection and jealousy led him to lash out against beautiful women and popular men.
Simon Astaire, the family friend, shed some light on the kind of person that Rodger was.
"As soon as you met him, he was unbearably reserved, self-contained; he seemed to merge into the walls," he said.
In one brief conversation, Rodger asked Astaire, a novelist, whether writing was a lonely experience.
Astaire described the process as "solitary," and Rodger replied with "I know what you mean" and turned away.
"He seemed the loneliest person in the world," Astaire said.
As the tragedy unfolded near the University of California, Santa Barbara campus, Rodger's parents were putting the clues together that it might be their son who was involved.
His mother received Rodger's manifesto, and after reading just four lines, she immediately went to YouTube to look at the videos her son had posted, Astaire said.
She watched the first 20 seconds of a video titled "Retribution" and then called her ex-husband. Both got on the road toward Santa Barbara as the shooting was unfolding.
The mother's fears were realized when she heard on the radio that a black BMW, like Rodger's, was involved.
"It was the longest journey of their lives and, I would suggest, everyone's nightmare," Astaire said.
Among the victims were Rodger's two roommates and a visitor, Cheng Yuan Hong, 20; George Chen, 19; and Weihan "David" Wang, 20. Each was stabbed to death.
But Rodger didn't stop there. He embarked on a shooting rampage Friday night, killing two young women: Katherine Cooper, 22, and Veronika Weiss, 19, both members of the Delta Delta Delta sorority.
He then went into a deli and killed UCSB junior Christopher Martinez, 20, who was getting a sandwich.
Martinez's father, Richard Martinez, has publicly called for stricter gun control laws.
One of the parents of a child killed in the Sandy Hook school shooting in Newtown, Connecticut, wrote an open letter to Richard Martinez.
The tragedy of losing a child to gun violence has made them part of the same extended family, Mark Barden wrote.
"My heart breaks for you because I know just a little about the long road ahead of you," he wrote, encouraging Richard Martinez to continue being an advocate for gun safety regulations.
"You will find your own path down this difficult road," Barden wrote. "But know that we are here for you and all of you who have been touched by this tragedy. Together we can and will build a safer world for all our children."
The firearms shop Shooters Paradise of Oxnard sold Rodger a gun just before the killings, manager Kevin White said.
Rodger had an Isla Vista address and wasn't acting strangely when he bought the gun, White said.
White, an alum of UCSB, said he spoke briefly with Rodger about Isla Vista.
There was a 10-day waiting period -- no red flags arose in the background check -- and then Rodger picked up the gun, White said.
The manager pointed out that a gun wasn't the only weapon used in the killings.
"It happens from time to time, but what about the guy who sold him the knives or the swords that he used, or what about the guy who sold him the car that he was driving around and hit people?" White said.
"Do they feel bad, or did they know he was going to do something bad with it? I mean, we sell tools. They're items. It's no different than the guy that sold him the knife that he used," White said.
CNN's Chris Cuomo, Greg Botelho, Holly Yan, Michael Martinez and Chuck Conder contributed to this report.