"We are crying in pain for the victims and their families. It breaks our hearts on a level we didn't think possible," the parents of Elliot Rodger said in a statement released to CNN.
"The feeling of knowing that it was our son's actions that caused the tragedy can only be described as hell on earth."
Rodger, 22, went on the rampage May 16 in Santa Barbara, California, after releasing a manifesto in which he claimed that his history of rejection by women made him want to take revenge.
His parents alerted police about their son several months ago, but authorities found no grounds to detain him or search his home for weapons.
The parents tried to rush to Santa Barbara after receiving Rodger's manifesto entitled Retribution, but by the time they arrived it was too late.
Among the victims were Rodger's three roommates Cheng Yuan Hong, 20, George Chen, 19, and Weihan "David" Wang, 20, all stabbed to death.
Rodger then opened fire on a campus sorority house, killing Katherine Cooper, 22, and Veronika Weiss, 19, and killed Christopher Martinez, 20, in a sandwich shop before taking his own life.
