Simon Astaire, in an interview Thursday with CNN, said the 22-year-old college student once asked him if writing is lonely. When Astaire, a novelist, responded that it is, Rodger replied, "I know what you mean."
"He seemed the loneliest person in the world," Astaire said.
Investigators say Rodger stabbed his three roommates -- Cheng Yuan Hong, 20, George Chen, 19, and Weihan "David" Wang, 20 -- and then went on a shooting spree near the University of California Santa Barbara campus. He killed Delta Delta Delta sorority sisters Katherine Cooper, 22, and Veronika Weiss, 19, as well as Christopher Martinez, 20, a UCSB student who was in a deli.
While Rodger left evidence of his violent plans, apparently inspired by a feeling he had been rejected by women, Astaire described him as quiet in person.
"As soon as you met him, he was unbearably reserved, self-contained, he seemed to merge into the walls," Astaire told CNN.
Rodger took his own life after crashing his BMW.
Astaire said Rodger's parents now won't talk about him. They are divorced, but both headed to Santa Barbara after seeing a manifesto and YouTube videos in which Rodger threatened violence.
"It was the longest journey of their lives and I would suggest, everyone's nightmare," Astaire said.
Celebrity Breakups and divorces of 2014 [PHOTOS]