Elliot Rodger, 22, went on an evening killing spree that began in his apartment and ended on the streets of Isla Vista, California. When it was over, Cheng Yuan "James" Hong, 20, Weihan "David" Wang, 20, George Chen, 19, Katie Cooper, 22, Veronika Weiss, 19, and Christopher Michaels-Martinez, 20, all lost their lives before Rodger turned his gun on himself.
Rodger, who had been in therapy since childhood, according to Simon Astaire, a writer and close friend of the Rodger family, had long caused his family concern.
"His father's conversations with me were always headlined by his concern for Elliot," Astaire tells PEOPLE.
Rodger's YouTube videos frightened his mother, Li Chin, so much that she called a mental health hotline – and six police officers visited her son's apartment on April 30. But he was deemed at that time "not a danger to himself or anyone else," Santa Barbara Sheriff Bill Brown said at a May 24 news conference.
But Friday evening, Chin received her son's 137-page manifesto outlining his plans, saw his disturbing "Elliot Rodger's Retribution" video and immediately called his father, her ex-husband Peter Rodger, as well as 911. Both parents raced to Isla Vista, near Santa Barbara.
"Within moments of watching the video, he said, 'We have to go to Santa Barbara,' " Astaire tells PEOPLE of Peter Rodger's reaction to his son's video. "They are so crippled with grief. Their pain is not just for the loss of their son. Their pain is greater for the innocent who didn't return on Friday night."
Reporting by HOWARD BREUER and MELODY CHIU
For much more on the victims and details of the murders, pick up this week's issue of PEOPLE, on newsstands Friday
Michael Nelson / EPA / Landov